Vitiligo treatment: a literature review

Introduction

Vitiligo is the most common depigmenting skin disorder, affecting 0.5–4% of the population and occurs equally in women and men [1–5]. However, women are more likely to seek medical help for this condition, probably due to aesthetic reasons and social factors [6]. Vitiligo occurs in both children and adults, with 1/4 of cases developing before the age of 10, and 3/4 of cases appearing before the age of 30 [6]. No predilection has been shown based on ethnicity or skin type [6]. Many theories have emerged regarding the pathogenesis of vitiligo. Currently it is classified as an autoimmune disease, with its pathogenesis linked to genetic, environmental, and metabolic factors, as well as oxidative stress and cell detachment abnormalities [7]. The characteristic skin lesion is an amelanotic white macule with distinct margins developing due to the loss of functional melanocytes in the skin, hair, or both [8]. Since 2011, thanks to an international consensus, segmental vitiligo (SV) has been distinguished from non-segmental vitiligo (NSV), what is considered one of the major successes of the consensus, due to the differences in prognosis depending on the type [6]. NSV, to which the classical term “vitiligo” refers, includes generalized, acrofacial (two most common), mucosal, universal, mixed and rare variants [6]. The diagnosis of vitiligo is generally based on clinical assessment (the presence of characteristic skin lesions in a typical distribution). A skin biopsy or other tests are not necessary except for excluding diseases that vitiligo can mimic [6]. The treatment of vitiligo is challenging and often requires a multi-directional approach. Methods include topical and systemic immunosuppressants, phototherapy and surgical techniques, which aim to either halt the progression of the disease, stabilize depigmented lesions, or stimulate repigmentation [6].

Methodology

The literature review was performed utilizing internet searching engine and available publications from the medical library. Literature search of the PubMed database was conducted to identify key articles on treatment of vitiligo published from 2012 to 2024. The keywords used in the search included “vitiligo”, “vitiligo, non-segmental”, “vitiligo segmental”, “vitiligo, pathophysiology”, “vitiligo, treatment”, “JAK inhibitor”, “vitiligo surgery”, “repigmentation” and “vitiligo, topical treatment”.

Topical therapy

In topical treatment, glucocorticosteroids and calcineurin inhibitors are most often used. This is the first-line treatment for vitiligo spots covering no more than 10–20% of the body surface [1, 3, 4, 5, 9–11].

Topical glucocorticosteroids

They are the first-line therapy. They act in an immunomodulating manner, inhibiting the activation of T lymphocytes, reducing the B-cell response to self-antigens and reducing the gene expression of many cytokines, such as IL-1, IL-2, IL-6, IL-8, GM-CSF, TNF-a or interferon-g [1, 3, 5]. Additionally, they stimulate melanocytes to produce melanin by attaching to the glucocorticoid receptor (GR), which affects the expression of the MLPH gene encoding melanophilin, which is involved in transporting melanosomes in the cell [5, 12]. The most commonly used glucocorticosteroids include betamethasone valerate, clobetasol propionate and mometasone [3, 5]. The stronger the steroid, the more often side effects may occur in the form of telangiectasia, skin atrophy, hypopigmentation, stretch marks, folliculitis and acne-like eruptions [5].
In segmental and non-segmental vitiligo, it is recommended to use potent and very potent corticosteroids once daily for 3–6 months, and if no improvement is observed after 3–4 months, the application should be discontinued. However, the duration of the treatment can be extended and the risk of local side effects minimized by using an intermittent scheme (e.g. 2 weeks on, 2 weeks off). The best results are achieved for skin lesions of the face and neck [10, 11].

Calcineurin inhibitors

Ointment with 0.1% or 0.03% tacrolimus or 1% pimecrolimus is recommended as an alternative to glucocorticosteroids in the case of vitiligo in the face area [1, 3]. Calcineurin inhibitors, like glucocorticosteroids, have an immunomodulatory effect. They influence cytotoxic T lymphocytes by inhibiting IL-2 and IFN-g, and reduce antioxidant stress in the organism. Satisfactory treatment effects are observed with combined therapy of tacrolimus with an excimer laser and pimecrolimus with NB-UVB therapy [5].
The therapy with calcineurin inhibitors should be continued for at least 6 months, with twice daily application, and if effective, prolonged up to 12 months or more [10, 11, 13, 14]. Moderate daily sun exposure is recommended during treatment [10]. Results are seen in segmental and non-segmental vitiligo cases [13, 14]. Similarly to steroids, the best results are seen in skin lesions of the face and neck. Increased probability of tacrolimus-induced repigmentation in those areas may be due to density of hair follicles [13]. In the case of treatment with calcineurin inhibitors, fewer side effects are observed than with topical glucocorticosteroids, especially in the case of atrophy and telangiectasia [3, 5]. However, therapy with topical calcineurin inhibitors is more expensive compared with topical steroids [14].

JAK inhibitors

Damage to melanocytes due to oxidative stress triggers the activation of the immune system, cytokine secretion, and antigen presentation, ultimately leading to the activation of cytotoxic T lymphocytes (CD8+), which exacerbate the damage to melanocytes [2]. IFN-γ and the genes it induces are critical to the activation of CD8+ T lymphocytes. Binding of IFN-γ to its receptor (IFN-γR) located on keratinocytes activates the JAK-STAT signalling pathway, leading to the release of CXCL10 chemokine, which promotes the migration of autoreactive T cells (CD8+), thereby contributing to the progression and persistence of vitiligo symptoms [2, 4, 15].
Disruption of IFN-γ signalling by inhibitors of Janus Kinases (JAK) contributes to repigmentation in patients with vitiligo [16]. The Janus Kinase family comprises four proteins (JAK1, JAK2, JAK3, TYK2), and ongoing tests on their inhibitors show promising results for the future therapy of vitiligo [16, 17]. Extensive research has been conducted on the use of tofacitinib and ruxolitinib in patients struggling with depigmentation.
These studies made ruxolitinib the first treatment for non-segmental vitiligo approved by the Food and Drug Administration (FDA) [11, 18].
Ruxolitinib is a JAK1/2 inhibitor initially developed for treating polycythaemia vera and primary myelofibrosis [16, 17]. The side effects of topical application of ruxolitinib are limited to the occurrence of erythematous changes, acne lesions or pruritus [11, 15, 18].
The treatment with 1.5% ruxolitinib twice daily is recommended in non-immunocompromised, patients over 12 years old with non-segmental vitiligo with depigmentation covering 10% or less of total body surface area, when other topical therapies are not sufficient or not advisable [9–11]. The use of ruxolitinib is associated with significant clinical improvements, with the best results in the skin lesions of the face, and minimal side effects compared with conventional topical steroids, calcineurin inhibitors, phototherapy, and depigmentation agents [11, 18].

Other topical treatments

Other pharmaceuticals used in the topical treatment of vitiligo include vitamin D analogues, prostaglandin analogues and antioxidants [1, 3, 5].
Topical vitamin D
According to some sources, the use of topical vitamin D analogues is not recommended, while others point to positive results in combination with topical steroids or in children [1, 3, 4, 5, 19].
Additional research in dosages and treatment duration is needed to maximize the benefits of vitamin D analogue usage in vitiligo patients. So far some studies have suggested that incorporating vitamin D analogues can help mitigate the side effects associated with corticosteroids [20]. In another research study, the delivery of calcipotriol and betamethasone was increased by using microneedling, with 76–100% repigmentation in 60% of patients. Moreover, this practice was effective in locations more commonly resistant to typical treatment methods of vitiligo such as elbows, knees, extremities and acral area [10].
Topical prostaglandin analogues
Topical prostaglandin analogues are used to treat glaucoma, and one of their side effects is discoloration. Research conducted so far shows that patients with vitiligo could benefit from the use of these drugs and their “side” effect, which becomes therapeutic for them [5].
Antioxidants
In the case of the use of antioxidants, there are no clear research results on their effectiveness in the treatment of vitiligo. It is suggested that they may have a beneficial effect when combined with short-term NB-UVB therapy or in combination with climatotherapy in the Dead Sea region [5].
In summary, topical treatment is best suited for localised disease, with vitiligo spots covering no more than 10-20% of the body surface. Furthermore, the side effects are rarely systemic. Nonetheless, even if improvement has been made with monotherapy topicals, the combination of different methods together is the most effective [11, 19, 21].

Phototherapy

Modern phototherapy methods had their origins many centuries ago, when solar exposure (heliotherapy) was used in combination with natural extracts of Ammi majus and Psoralea corylifolia plants [22]. In recent years, photochemotherapy (PUVA (psoralen and ultraviolet A)), which is a combined therapy with a drug from the psoralen group followed by exposure to UV rays with a wavelength of 320–400 nm with a peak at 365 nm, has been at the forefront in the dermatological treatment of vitiligo. Currently, due to unavailability of 8-methoxypsoralen (methoxsalen) this method is no longer in use in Poland.
According to the recommendations, the indications for using phototherapy include early localized vitiligo or with signs of rapid progression, active or stable non-segmental vitiligo, segmental vitiligo, stable localized non-segmental vitiligo and non-segmental vitiligo in light skin [11].
Due to the greater safety of the method and better results, NB-UVB 311 nm therapy (narrowband UVB 311 nm phototherapy) is currently considered the treatment of choice in vitiligo, particularly for widespread or rapidly progressive disease [11]. In the case of lesions covering more than 20% of the skin surface, it is recommended to irradiate the entire skin, while for focal lesions the following are used: targeted phototherapy with a 308 nm excimer laser, 308 nm excimer lamp or focal phototherapy with 311 nm (comb lamp) [4].

NB-UVB

The administration of radiation doses depends, among other factors, on the skin type. It is recommended to start treatment with an initial dose of 200 mJ/cm² for light skin populations and 400–500 mJ/cm² for darker skin populations [11, 23]. Each dose is increased by 10% to 20%, or maintained, depending on the severity of erythema, with a maximum dose of 1500 mJ/cm² for the face and 3000 mJ/cm² for the body [11, 23]. Positive predictive factors include younger age (especially paediatric), recent onset of the disease, localization on the face and neck and, during treatment, the presence of perifollicular pigmentation on dermoscopy [11]. There is no consensus about the maximum allowed number of sessions, however, to limit cumulative exposure risks, experts recommend that phototherapy should be stopped if there is no improvement after 3 months or unsatisfactory results after 6 months [11]. According to the Vitiligo Working Group, after complete repigmentation tapering has been suggested in the following schedule: twice a week for a month, then once a week for a month, then once every other week for 2 months, then stop [11].
The advantage of NB-UVB is its ability to halt disease progression and induce repigmentation. Thus, early initiation of NB-UVB is particularly useful in cases of segmental and acral vitiligo, where achieving repigmentation in the later stages of the disease is difficult [11]. Another advantage of this method over other forms of phototherapy lies primarily in the more favourable side effect profile of this method, including the safety of its use in pregnant and breastfeeding women [22]. The most commonly observed side effects of NB-UVB therapy are erythema, xerosis, skin pruritus and burn injury [11, 23].

Excimer devices

In some vitiligo forms the excimer laser and lamp have an advantage over NB-UVB. Excimer devices, as mentioned earlier, should be considered in cases of localized disease. However, opinions are divided on whether this is the treatment of choice for segmental vitiligo [11]. According to Bae et al., a combination therapy with 308-nm excimer laser, topical tacrolimus, and short-term systemic corticosteroids turned out to be effective in SV [24].
The irradiation should begin with an initial dose of 100 mJ/cm² and be gradually increased weekly by 10–25% [11]. Patients should receive three sessions per week, but the overall response to treatment is determined by the total number of sessions completed, not the frequency of the sessions [11, 25].
The advantages of these methods include shorter required treatment duration and a lower risk of darkening of non-lesional skin in surrounding areas. The risk of adverse effects such as erythema and blistering is largely operator-dependent, and with experienced personnel, the safety and tolerance of this method are comparable to NB-UVB [11].
A disadvantage of this method is the significant time consumption when treating extensive lesions. Additionally, the cost of such therapy is usually higher [11].

Combined therapy

The literature suggests that patients with significant disease progression should be treated using a combination of different methods. Studies show that the most favourable outcomes in this group of patients are achieved using a combination of systemic treatment and phototherapy. Combination with topical glucocorticoids allows for faster repigmentation [26], while the use of glucocorticoids generally inhibits disease progression [27]. Authors suggest combining systemic steroids in the form of mini-pulses with NB-UVB therapy, for example in the following regimen: methylprednisolone at a dose of 16 mg (or dexamethasone at a dose of 5 mg) for 2 consecutive days and NB-UVB 2–3 times per week for 6 months. Such a combination prevents disease relapses in over 80% of cases [28].
In summary, phototherapy is considered a method that requires a long duration of use to achieve noticeable effects; the minimum treatment duration is 6 months [29]. Before starting therapy, patients should be informed about this, and then motivated to achieve the maximum treatment response. The best response to phototherapy is observed in lesions located on the face and neck, while the worst response occurs in acral lesions. In the treatment of extensive lesions, NB-UVB should be chosen, while for more localized changes, excimer devices are recommended. Combining phototherapy with other therapeutic methods can significantly increase the chances of therapeutic success, leading to better treatment outcomes. By using combination therapy, such as topical medications or systemic steroids, better repigmentation and faster results can be achieved compared to phototherapy alone [28, 29].

Laser therapy

In addition to the above-mentioned 308-nm excimer laser, according to the literature, helium-neon lasers (632.8-nm), fractional CO₂ laser and other could also be used [5, 30]. Lasers in vitiligo therapy are exploited in various ways, from repigmentation, through patient preparation for surgery, to depigmentation procedures described below. In monotherapy, it is possible to achieve repigmentation with an excimer laser (308-nm) and a titanium-sapphire laser (311-nm). There are also positive effects of the combination of local calcineurin inhibitors with an excimer laser and NB-UVB therapy with fractional lasers.
The laser’s mechanism of action is based on the release of cytokines and growth factors that act as mitogens for melanogenesis and the creation of controlled micro-injuries in the outer layers of the skin. Due to the created micro-pores, the efficacy of topical medications and UV radiation is significantly enhanced [31]. The fractional CO₂ laser, used as a complement to other methods, appears to be a promising treatment for refractory vitiligo and lesions located in acral areas (hands and feet), as well as on bony prominences (elbows and knees). However, the authors emphasize that more detailed analyses and studies are needed [32].
In a 2018 study by Kim et al., the effectiveness of fractional CO2 laser in combination therapy for treating refractory vitiligo was demonstrated (RR = 4.9; 95% CI: 1.15–20.93; p = 0.03) [31]. Participants were treated with the laser using the following settings: pulse energy of 100 mJ, spot density of 150–200 spots/cm², and two passes over the designated area. The duration of the therapy ranged from 2.5 to 5 months. As conventional therapy, topical medications (topical steroid, topical salicylic acid), phototherapy (UVB), sun exposure and surgical treatment (autologous hair transplant) were used in various combinations [31].
When preparing a patient for transplantation, it is worth paying attention to a short-pulsed CO₂ laser (emitting short pulses of high-energy 10,600-nm radiation), a fractional CO₂ laser and an Er:YAG. Their use before the transplant increases the chance of its proper nutrition and implantation, as well as the final satisfactory aesthetic effect.
Ultimately, laser methods provide satisfactory results for patients, with few complications and adverse reactions. However, these methods are expensive, not available in every hospital and only suitable for use on a small area of skin [30].

Depigmentation therapy

Depigmentation therapy should only be considered for patients with areas of healthy skin not exceeding 20% of its surface area [4]. When depigmentation is chosen as a treatment method, monobenzyl ether of hydroquinone (MBEH), phenol peels, cryotherapy, and various wavelength Q-switched nanosecond lasers (532, 694, 755 nm) (ruby and alexandrite) are used. The best results are achieved during the active phase of vitiligo, particularly when the Koebner phenomenon is present [4, 5, 33].
MBEH is used as a 20% cream applied once or twice daily. Its mechanism of action is related to the production of reactive oxygen species (ROS), and achieving depigmentation may take from 4 to 12 months. Moreover, it is associated with local side effects, like contact dermatitis, pruritus and distant depigmentation, as well as the risk of repigmentation. Lasers can be used in cases where MBEH or other bleaching agents have failed, and can be appropriate when rapid depigmentation is desired, in areas such as the face. However, the main drawbacks in their use include the discomfort experienced by the patient (local anaesthesia is needed) and the availability of equipment in the medical facility. Cryotherapy allows for rapid repigmentation, especially in patients susceptible to Koebner phenomenon. It is inexpensive and safe but requires the physician to have experience in performing the procedure. Additionally, it is suitable only for small lesions [34, 35].
Due to potential sociocultural issues, depigmentation therapies should be carefully considered and used only in appropriately selected candidates. Additionally, since each method has its own side effects, patients should also be informed about them [34, 35].

Systemic treatment

Glucocorticosteroids

Glucocorticosteroids are used in patients with unstable vitiligo, which can be determined by appearance of new lesions or deep pigmentation on fingertips and toes [1, 3, 11, 14, 21]. Topical treatment in a very active form of disease will be ineffective, and therefore stabilization of the disease is so important. The systemic treatment may include mini-pulse therapy with dexamethasone 2.5–5 mg or betamethasone 5 mg twice weekly on 2 consecutive days per week, with maximum duration up to 6 months, but preferably for 3–4 months [11, 14]. Combination of betamethasone or dexamethasone with NB-UVB may present with a higher degree of depigmentation [1, 11].
However, common problems with this treatment include deterioration of symptoms after discontinuation of therapy and adverse effects such as weight gain, insomnia, agitation, acne, menstrual disturbances, hypertrichosis, growth retardation in children and immunosuppression, which have to be discussed in detail with the patient [11].
Nevertheless, there are promising data for oral Janus kinase (JAK) inhibitors to stabilize vitiligo, which will be discussed below [21].

Cyclosporine A

Cyclosporine A is an immunosuppressive drug that, by blocking calcineurin, prevents the activation of the nuclear factor of activated T cells (NFAT), crucial for the transcription of genes responsible for synthesizing interleukin 2 (IL-2), which plays a role in T cell activation. Through this mechanism, cyclosporine A inhibits the immune response and chronic inflammatory processes. Taneja et al. [36] examined 18 patients with progressive acquired vitiligo, administering cyclosporine A orally at a dose of 3 mg/kg body weight per day in two divided doses over 3 months, showing a statistically significant reduction in the severity index of the disease, VASI (Vitiligo Area Scoring Index). The most effective outcomes of the treatment were observed on the affected areas of the neck and upper chest skin. The treatment was well-tolerated; however, due to known drug interactions and adverse effects of cyclosporine A, such as nephrotoxicity, metabolic disorders, or gingival hypertrophy, therapy with this medication requires proper monitoring [5].
In conclusion, the results with topical treatment are impossible to obtain in a patient with active and unstable vitiligo. Stabilization of the disease is possible with oral glucocorticosteroids and there are promising studies on other systemic treatments. However, the use of steroids is associated with a great number of side effects and no possibility of long-term therapy [11, 14, 21].

Surgery

Surgical treatment plays a particularly important role in the therapy of vitiligo resistant to other forms of treatment, but in the case of vitiligo patches located on the backs of hands and feet, it represents the method of choice. A prerequisite is disease stabilization, defined as a 6-month period without progression (i.e. the appearance of new vitiligo patches or enlargement of existing ones) [4]. Surgery should be reserved for patients with documented failure of medical interventions, especially in patients with SV and stable, localized NSV. There are two main groups of surgical methods – tissue grafts and cellular grafts. However, the procedure for each treatment varies significantly depending on the size and location of the lesions [11].

Tissue grafts

Autologous mini-punch grafting (MPG) is a method that involves directly transferring 1–2 mm punch grafts from donor sites to recipient sites [11] and is recommended especially for patients with acral vitiligo or vitiligo involving the areas around the mouth, hands, nipples and when vitiligo patches have irregular shapes [37]. It is the simplest and the most affordable method, however, it is relatively time-consuming. For larger lesions, motorized 0.8-mm punch can be used [11]. A disadvantage of this method is a risk of developing a morphological complication in the form of cobblestone appearance [11, 34]. To avoid this complication, it is recommended to use thin grafts containing only the superficial layer of the papillary dermis, while in treatment, the ablative CO₂ laser appears to be effective [34].
Grafting of the epidermis from a suction-induced blister (Suction Blister Epidermal Grafting, SBEG) is a method requiring no specialized additional equipment (only syringes and a vacuum). It gives excellent cosmetic results and is suitable for use in sensitive areas such as around the mouth (including corners) and eyelids. Additionally, it is characterized by minimal scarring at the donor site and can be used in conjunction with subsequent phototherapy [11, 37, 38]. This method also has its drawbacks; the technique of harvesting grafts by creating a blister can be painful (local anaesthesia is used) and in case of extensive lesions, it is time-consuming [11].
Both punch skin grafting (PSG) and SBEG are considered effective treatments for lip vitiligo. However, PSG provides a better cosmetic outcome in terms of the lip colour [39].
Hair follicle grafts are based on the theory [40] that inactive melanocytes with DOPA-negative cells are present in the outer sheaths of hair follicles in patients with vitiligo. These cells have the ability to produce melanin under the stimulating action of UV rays. Rectangular skin fragments are taken from the occipital or temporal skull area and then transplanted into the vitiligo-affected area. Ten days after the transplant, the use of tacrolimus, glucocorticosteroids, or photochemotherapeutic methods should be considered as supportive treatment. This is a simple and relatively low-cost method, but it carries the risk of adverse reactions such as foreign body granuloma formation [37].
In addition to tissue grafting methods mentioned above, others such as: split-thickness skin grafting (STSG) and its modification known as smash grafting, epidermal curettage technique (ECT) and the flip-top method exist.

Cellular grafting

The primary cellular methods include the transplantation of cultured melanocyte graft and a similar method, the transplantation of cultured epidermal graft [37, 41]. This is a modern procedure in the field of regenerative medicine, involving the extraction of melanocytes from the patient’s healthy skin area, followed by cell cultivation in laboratory conditions with the assistance of specific enzymes. After obtaining a significant number of melanocytes, they are transplanted into the areas affected by vitiligo, stimulating the skin in that area to produce melanin [41]. The advantage of this type of graft is the need to extract only a small portion of healthy skin, along with its effectiveness and safety, which distinguishes it among other surgical methods [37].
According to Bassiouny et al., autologous non-cultured melanocyte–keratinocyte transplantation procedure (MKTP) is one of the simplest and currently most popular cellular transplantation technique [42]. Over the years, this method has undergone numerous modifications aiming to improve its effects and reduce the overall technique duration [37]. The procedure involves placing the harvested skin fragment in a trypsin solution, which, after incubation, allows for the separation of the epidermis from the dermis, followed by isolating melanocytes and keratinocytes in a suspension to be transplanted into the patient. Depending on the modification, the entire procedure takes 1–2 days. The success of the therapy largely depends on appropriate selection of patients for treatment [37, 42].
The non-cultured follicular root sheath suspension method involves obtaining a single-cell suspension of melanocytes by harvesting a skin fragment and using pressure dressings. Transplanting this way obtained cells into vitiligo patches yields highly satisfactory results, achieving over 90% repigmentation in 60% of patients. The method is considered a safe, minimally invasive and scarless with excellent pigmentation and satisfactory colour matching the recipient. Among side effects in the recipient area, asymptomatic erythema and hyperpigmentation can occur [5, 43].
In conclusion, the general advantage of surgical methods is the lack of systemic side effects that may discourage some patients from undergoing treatment with medications [44]. The main drawback of tissue grafts is the alteration of skin texture and scarring at the donor site. In this group, the lowest risk of such complication is provided by SBEG [44]. Cultured and non-cultured epidermal suspensions are more complicated and time-consuming, while SBEG is one of the simplest methods. Colour mismatching (hypo- or hyperpigmentation) is a complication that can occur with any methods [45]. Large area lesions can initially be addressed with cellular grafting, and then tissue grafting can be used for the smaller remaining areas [46]. Pigment cell transplantation is most effective in patients with stable segmental vitiligo. In patients with non-segmental vitiligo, pigment cell transplantation has a higher chance of an acceptable repigmentation if the disease is stable for at least 1–2 years and no Koebner phenomenon is present [11]. The appropriate selection of candidates for surgical methods in vitiligo treatment is crucial for therapeutic success. Studies show that the best results (repigmentation > 90%) are achieved by young patients with segmental vitiligo in non-acral area [46].

The future of vitiligo treatment

Systemic immunomodulatory treatment

The literature describes attempts to use antibiotics with immunomodulatory and anti-inflammatory properties in the treatment of vitiligo. In randomized controlled clinical trials, patients were administered minocycline based on its anti-apoptotic properties, modulation of matrix metalloproteinases, and its impact on cytokine production. The effect of daily oral intake of 100 mg of minocycline over a period of 6 months in inhibiting disease progression was comparable to the therapy involving corticosteroid mini-pulses [5, 47].

Methotrexate

Methotrexate is a cytostatic drug belonging to the antimetabolite group and a folate antagonist used in the treatment of many autoimmune diseases. The theory behind the effectiveness of methotrexate in treating acquired vitiligo is its influence on reducing the number of T lymphocytes responsible for producing tumor necrosis factor-α (TNF-α). A prospective randomized open-label study involving oral intake of 10 mg of methotrexate once a week for 6 months demonstrated comparable efficacy of this approach to administering dexamethasone orally at a total weekly dose of 5 mg. The best effects were observed in vitiligo patches located in sun-exposed areas, while the weakest response to methotrexate treatment was noted for changes in mucous membranes, hands, and soles. The treatment was well-tolerated by patients [5].
In another study involving patients with localized, non-segmental vitiligo, participants were divided into three groups. In Group 1, only a 1% methotrexate gel was applied topically twice a day. In Group 2, the same 1% methotrexate gel was applied topically twice a day, but combined with NB-UVB therapy twice weekly, starting at a dose of 200 mJ/cm², increasing the dose by 10–20% with each session. In Group 3, the 1% methotrexate gel was applied topically twice a day, combined with treatment using an excimer lamp, starting with a dose of 100 to 150 mJ/cm² for the head and neck, and 200 to 600 mJ/cm² for other areas of the body. The dose was increased by 50 mJ/cm² per session. The treatment lasted for 3 months, with monthly follow-ups. A statistically significant difference was achieved between the studied groups, with the best response observed in Group 2 (methotrexate combined with NB-UVB), where the mean percentage of repigmentation was 49.7 ±33.5. Importantly, methotrexate was found not to be effective enough to induce repigmentation when used alone (in Group 1, the mean percentage of repigmentation was 19.3 ±20.7) [48].
Known adverse effects of methotrexate include hepatotoxicity and myelosuppression, therefore close monitoring of liver parameters and blood morphology is necessary during therapy [5].

JAK inhibitors

The Jak inhibitor, ruxolitinib, was presented in the previous part, however further attempts using additional kinase inhibitors are emerging, such as [17, 21]:
• baricitinib, a JAK1/2 inhibitor currently used in the treatment of rheumatoid arthritis,
• ifidanctinib (ATI-50002), a JAK1/3 inhibitor showing effects in treating alopecia areata,
• ritlecitinib (PF-06651600), a JAK3 and tyrosine kinase inhibitor used in rheumatoid arthritis,
• brepocitinib (PF-06700841), a TYK2/JAK1 inhibitor,
• cerdulatinib (PRT062070), a SYK/JAK inhibitor,
• tofacitinib,
• povorcitinib.

Tofacitinib and povorcitinib

Tofacitinib is a JAK1/3 inhibitor currently approved by the FDA for treating active ulcerative colitis, rheumatoid arthritis, and psoriatic arthritis [17]. It can be administered orally or topically [15, 17]. Unfortunately, its oral form carries the risk of severe systemic complications such as cytopenia, carcinogenesis, and recurrent infections [17]. Side effects are associated with the fact that a deficiency of JAK3 protein leads to a JAK3-deficient severe combined immunodeficiency (SCID) [16]. Therefore, topical treatment might be preferred, especially in combination with NB-UVB therapy [15, 17].
The phase 3 trials are currently being conducted on oral JAKs and their efficacy in vitiligo treatment. Promising results were observed in unstable vitiligo cases treated with 45 or 75 mg of povorcitinib. In the future the oral JAK inhibitors could be an alternative to steroids, with also faster stabilization of the disease [21].

STAT inhibitors

Statins or HMG-CoA reductase inhibitors are commonly used to lower cholesterol levels in patients. In vitro studies have noted their role as inhibitors of STAT1 molecules, and studies on mouse models have shown that simvastatin not only halts further depigmentation but also possesses repigmenting properties. Repigmentation was first observed in a 55-year-old patient undergoing treatment for uncontrolled arterial hypertension. Unfortunately, the second phase of clinical trials regarding the use of simvastatin in vitiligo treatment did not yield the expected results. Discrepancies in the outcomes compared to the mouse model might stem from potential toxicity of the drug at higher doses. Further studies are ongoing on the topical application of simvastatin and atorvastatin, aiming to overcome the systemic toxicity issue associated with high oral doses [15].

New phototherapy methods

A novel tool in combating acquired vitiligo through phototherapy is the UV-A1 laser. It is characterized by deeper skin penetration and immunomodulatory properties. It regulates the formation of reactive oxygen species (ROS) during oxidative phosphorylation in mitochondria, causing damage to DNA, proteins, lipids, and cell organelles, which may intensify the inhibition of the immune response and stimulate melanogenesis. A study involving 17 patients showed a good or excellent response in 53% after 8 weeks of treatment, with effects persisting after 12 weeks [5].
In another study, 30 patients with acquired vitiligo (average age: 34 years) underwent therapy using the fractional Erbium laser (the original spelling from citation [49] is “Fraxel Herbium laser”) in combination with topical latanoprost and UV-A1 laser. Initially, patients were subjected to a single dose of fractional Erbium laser at a wavelength of 1540 nm (1800 mJ/cm²), followed by the application of 0.005% latanoprost (1 drop per 2.5 × 2.5 cm² of the affected area). The next day, the affected areas were exposed to UV-A1 laser (Alba 355 nm) for 20 minutes. The therapy was repeated every 21 days for 9 months, achieving > 75% repigmentation in 90% of patients, with an average repigmentation of 88%. The only reported side effects were transient inflammation and erythema [5, 49]. However, lasting repigmentation was not achieved [5].

Combined therapy in RCM imaging

Studies show that combined therapy, involving surgical treatment and phototherapy, is more effective than monotherapy. A significant role in this combined method is played by the reflectance confocal microscopy (RCM), which has multidimensional usefulness. First, it allows for the differentiation between active and stable vitiligo (indicating whether surgical methods can be applied). Second, it enables the assessment of treatment outcomes and the level of repigmentation achieved. Unfortunately, there is a lack of specific guidelines and validated protocols on how to best combine these methods, and the literature on this topic is currently insufficient [45].

Combined phototherapy-JAK inhibitors treatment

Research is ongoing on the effects of combining NB-UVB with JAK inhibitors. In research models, JAK1/3 inhibitors (tofacitinib) and JAK1/2 inhibitors (ruxolitinib) inhibit inflammatory and autoimmune processes, making stimulation of melanocytes possible at low doses of NB-UVB [22]. In one study, additional benefits in terms of skin repigmentation were demonstrated when ruxolitinib was combined with NB-UVB compared to phototherapy alone [50, 51].

Combined phototherapy-afamelanotide treatment

Studies are currently underway to explore the combination of phototherapy with afamelanotide. Afamelanotide is a synthetic analogue of a-melanocyte-stimulating hormone (α-MSH) that acts as an agonist on the melanocortin-1 receptor (MCR1). In the form of a subcutaneous implant, it is used to prevent sensitivity to sunlight in patients with erythropoietic protoporphyria. NB-UVB has the ability to stimulate melanoblasts and stem cells in the hair follicle niche to express MC1R receptors, preparing them for binding with afamelanotide. Afamelanotide, as a direct source of α-MSH, significantly accelerates the repigmentation process initiated by the phototherapy. Studies have shown that the fastest repigmentation was achieved on the face and upper extremities. However, a limitation of the method was its lack of effectiveness for skin phototypes other than IV to VI [50, 52].

Cytokine-targeted therapies

In vitiligo various monoclonal antibodies can be used. However, most of them are still in the research phase. This group includes antibodies directed against IFN-γ, CXCL10, CXCR3, HSP70i, IL-15, IL-17/23 and TNF-α [17].

IFN-γ, CXCL10, CXCR3

As partially mentioned above in the section of JAK inhibitors, the IFN-γ-CXCL9/10-CXCR3 axis may be crucial in the pathogenesis of vitiligo and contribute to disease progression by inhibiting melanogenesis, inducing melanocyte apoptosis and further T cell recruitment [2, 4, 15, 17].
Currently, anti-IFN-γ antibodies are used, among others, in the treatment of rheumatoid arthritis, multiple sclerosis, autoimmune skin diseases, and in the prevention of corneal rejection after transplantation. Studies conducted so far on mice and patients have yielded positive results, with repigmentation and reduction in the size of vitiligo lesions. The patients received the drug in the form of subcutaneous injections in the area of the lesion. Further research is required on the role of IFN-γ in the pathogenesis of vitiligo and the cost-effectiveness of its neutralization using monoclonal antibodies when topical drugs with the same mechanism are already available [5, 16, 17].
The lack of CXCL10 reduces the severity and incidence of vitiligo [16]. This chemokine is primarily involved in the migration of T lymphocytes, triggering the infiltration of immune cells at an early stage of the disease. The CXCL10 protein is also involved in reducing the amount of NMB (non-metastatic melanoma protein B) glycoprotein. Studies conducted on mice suggest CXCL10 suppression as the right direction in the search for new therapeutic strategies [17]. However, among melanoma patients, higher CXCL10 expression is associated with better prognosis [53].
The receptor for CXCL10 and CXCL9 ligands, involved in the pathogenesis of vitiligo, is the CXCR3 receptor located on T lymphocytes [16]. The binding of the ligands to the receptor leads to further recruitment of CD8+ lymphocytes, secretion of IFN-γ, TNF-α, and further to the progression of lesions [2, 4, 15–17]. After using antibodies against CXCR3 for 7–8 weeks in laboratory mice, vitiligo lesions became less severe, especially in the perifollicular areas. These are preliminary results, however justify further research on CXCR3 targeting [17].

HSP70i

Inducible heat shock protein 70 is regulated by stress and protects cells against apoptosis. It is also released by melanocytes and constitutes an alarm signal for dendritic cells that ensure immunological tolerance [54]. Previous studies have shown that HSP70i mRNA expression in skin lesions of patients with vitiligo is higher and correlated with disease activity. An increase in HSP70i expression alone is sufficient to induce depigmentation in animal models. So far, tests using HSP70iQ435A DNA, both in mouse and Sinclair pig model, have shown significant repigmentation also associated with an increase in the CD4/CD8 ratio and stopping the accumulation of T cells. The delivery of HSP70iQ435A DNA has the potential to become an effective therapeutic intervention in the future treatment of vitiligo [17].

IL-15 inhibitors

IL-15 most likely participates in the regulation of IL-17 and TRM cells (tissue-resident memory CD8+ T cells), which are responsible for long-term symptoms of vitiligo and potentially for its relapses. Anti-CD122 antibody, which targets IL-15 signalling, effectively reverses depigmentation in laboratory mice. Anti-CD122 treatment, both systemic and topical, reduces TRM-induced IFN-γ production, resulting in long-term repigmentation [17].

IL-17/23 and TNF-a inhibitors

In the case of IL-17/23 and TNF-α, a correlation can be observed between their levels and disease activity. With the treatment of patients with vitiligo, the activity and titre of the above cytokines also decreases. This resulted in the initiation of research on the use of IL-17/23 and TNF-α inhibitors in the treatment of vitiligo. Unfortunately, the results of research conducted so far are unsatisfactory [15–17]. Although trials with ustekinumab (inh IL-23) or etanercept (inh TNF-α) resulted in disease stabilization or even repigmentation, other trials did not prove the benefits of using inhibitors of these cytokines. Some of the studies even had to be completed earlier due to significant disease progression among patients receiving secukinumab (inh IL-17), ixekizumab (inh IL-17A) and adalimumab (inh TNF-α) [15, 17].

Immune checkpoint modulators

Immune checkpoints are molecules that regulate the response of T lymphocytes to the inflammatory process. These molecules include programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). Different preparations that affect these molecules are used in oncology, for example for metastatic melanoma. The mechanism of their action gives grounds to suspect that selective activation of surface molecules could rebuild tolerance in patients suffering from vitiligo [15]. Studies on the use of abatacept in vitiligo patients are ongoing. It is a recombinant fusion protein composed of a CTLA-4 fragment and a modified Fc fragment of human IgG1 immunoglobulin, currently registered for the treatment of rheumatoid arthritis (RA) [15, 55].

Therapies targeting regulatory T cells (Tregs)

Regulatory T cells (Tregs) have CD4+ molecules on their surface, act as a suppressor against autoreactive T cells, and produce, among others, IL-10 and TGF-b [56]. In vitiligo, there is reduced expression of the FoxP3 transcription factor (a marker specific for Treg lymphocytes) and decrease in Treg lymphocytes within lesional, non-lesional, and perilesional sections [5, 17, 57]. This gives rise to the suspicion that increasing the number of normal Treg lymphocytes may be a promising therapeutic method for vitiligo. Current strategies to use those cells in therapy include polyclonal Treg lymphocytes, antigen-specific Treg lymphocytes or genetically engineered Treg lymphocytes. Research models of vitiligo in mice have demonstrated the short-term effectiveness of polyclonal Treg cell transfer. A significant delay in the development of depigmentation was also found in TCR (T-cell receptor) transgenic mice that received CAR (chimeric antigen receptor) Treg cell treatment. The disadvantage of this method is the technical difficulty of introducing purified Treg cell populations into specific target cells. The solution to this problem may be the topical application of Treg cells or the combination with CCR4 Treg homing receptor CCL22 through needle-free DNA injection or the use of plasmid DNA encoding CCL22 [17]. Another method, involving use of neomycin, turned out to significantly delay depigmentation in the course of vitiligo in mice, as a result of the infiltration of Treg cells into the skin [17, 58]. A different study used hemin, an HO-1 agonist (a functional modulator of Treg cells). Hemin improved the recovery of Treg cell function by acting through HO-1 and upregulating IL-10 expression [17, 59]. The study results suggest the potential use of HO-1 in the future treatment of vitiligo [59].

Topically administered immunosuppressive drugs

Methotrexate has pro-apoptotic, anti-inflammatory and immunomodulatory effects, it probably modifies the expression of interleukin 6 (IL-6), the production of reactive oxygen species, and also inhibits the TNF-a-dependent activation of NF-kB. In the case report of a 23-year-old patient with localised vitiligo, after exhausting other therapeutic options, it was decided to start the treatment with methotrexate gel 1% administered twice daily for 12 weeks. After completing the treatment, significant repigmentation was observed with no local or systemic side effects [5].
Another clinical study described topical treatment with mycophenolate mofetil in 30 patients suffering from localised vitiligo [5]. Mycophenolate mofetil 15% was applied twice daily for 3 months, achieving minimal repigmentation in approximately 36% of patients. The treatment results were not satisfactory and showed lower effectiveness compared to local steroids [60]. However, the authors emphasize the favourable safety profile of this method [5, 60].

New therapies targeting micro-RNA (miRNA)

Micro-RNAs are non-protein-coding RNA molecules consisting of 20–24 nucleotides that regulate the level of translation in the cell. Numerous studies conducted on these particles have shown, among others, their impact on genetic polymorphism, oxidative stress and melanocyte functions [17]. The role of miRNAs in the connections between melanocytes and the non-specific immune response is also postulated [2]. The involvement of miRNAs in the regulation of the expression of genes determining the function of melanocytes suggests that these molecules may play an important role in the treatment of vitiligo, serving as a target for new drugs. The first strategy involves the use of anti-miRNA, locked nucleic-acid (LNA), to prevent excessive miRNA activation. STTM (short tandem target mimic) – miR-508-3p up-regulates the expression of SOX6, increasing the expression of key genes for melanogenesis (CREB, MITF, TYR, TYRP1/2), as well as MYO5A, increasing the level of MITF, TYR, TYRP1, melanin and Rab27a. The second strategy involves replacing miRNA by restoring a non-allelic miRNA suppressor gene or using the gain-of-function of miRNA mediated by parvovirus (AAV) to regulate gene expression. The study showed that the migration ability of melanocytes changed under the influence of the non-allelic gene miR-211 acting through the p53-TRPM1/miR-211-MMP9 axis [17].

Conclusions

Vitiligo is a challenging disease to treat, and therapies often require modification or combination with other methods. There are many different options available, and therapeutic success primarily depends on the correct selection of the method suited to the patient’s individual medical condition. There are specific factors that assist doctors in limiting the selection to a particular set of methods. Topical treatments are most appropriate for localized cases, while systemic therapies should be started for unstable conditions. Light-based therapies, particularly NB-UVB, serve as important adjuvants, especially for children, pregnant women and individuals with significant systemic co-morbidities, to reduce the risk of adverse effects. Available treatment regimens for vitiligo are often insufficient. However, the more we understand the pathophysiological processes underlying vitiligo, the greater the chances of discovering more targeted, effective, and safer therapeutic methods. Many studies are currently being conducted in the field of vitiligo treatment (some of them are summarized in table 1). New methods, such as biologic medications, represent a promising form of treatment as they typically offer maximum efficacy with minimal side effects. Further research is still needed in vitiligo treatment to develop specific guidelines that encompass both existing and new treatment options, providing satisfactory outcomes for this challenging condition [5, 14, 50, 61].

Funding

No external funding.

Ethical approval

Not applicable.

Conflict of interest

The authors declare no conflict of interest.

References