Blaschkoid extragenital lichen sclerosus: an exceedingly rare presentation

Lichen sclerosus (LS) is a chronic inflammatory disease of uncertain etiology affecting skin and mucosal surfaces. Majority of the cases (around 85%) involve the genital area while extragenital cases are encountered less frequently (15–20%). Genital LS can occur simultaneously with extragenital LS; however, only in 6% of the cases, the extragenital type has been described to occur in isolation [1, 2]. Classically, extragenital LS affects sites which include neck, upper trunk, and shoulders [3]. Only a handful of cases of extragenital LS following lines of Blaschko (LB) have been described in the literature [2]. In this article, the author reports a case of extragenital LS in a Blaschkoid pattern, an exceedingly rare presentation. Additionally, a tabulated review of the published cases of Blaschkoid LS has been presented and dermoscopic findings and treatment of extragenital LS have been discussed.
A 40-year-old male presented with multiple asymptomatic whitish papules on his chest in a U-shaped distribution which he noticed 3 months ago. Initially, the lesions appeared on the right side of the chest and progressed further crossing the midline to involve the left side of the chest as well. He denied any past or family history of similar looking lesions. On examination, there were multiple small discrete rounded depigmented atrophic macules and papules of variable size (1–3 mm in diameter) which were present in a U-shaped pattern along the lines of Blaschko on both sides of the chest (figs. 1 A–C). Dermatologigal examination did not reveal any changes of hair, nails, oral and genital mucosae. Systemic examination was non-contributory. KOH wet mount did not reveal any fungal elements. Routine laboratory tests including ANA and Borrelia serology were unremarkable.
Dermoscopy showed white structureless areas with telangiectasia (figs. 2 A, B). Punch skin biopsy showed epidermis with compact ortho-hyperkeratosis with follicular plugging. Stratum Malpighi was atrophic with effacement of rete ridges. Upper dermis showed sclerosis and homogenization of collagen with diffuse lymphocytic infiltrate. Dilated capillaries with mild perivascular lymphocytic infiltrate were present in the mid dermis (fig. 3). Clinical, dermoscopic and histopathological correlation was consistent with Blaschkoid extragenital LS. The patient was prescribed topical tacrolimus 0.1% ointment to be applied twice daily and is still under follow up.
Lines of Blaschko (LB)...


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