Reflectance confocal microscopy findings of clear cell papulosis and histopathological correlation

Clear cell papulosis (CCP) is a rare skin disease which predominantly develops in Asian population during their early childhood especially under 6 years old. Since it was first recognized by Kuo et al. [1], there have been more than 50 cases of CCP published in the literature. The disease is characterized clinically by a number of asymptomatic white or hypopigmented papules which are mainly in the lower part of the abdomen and pubic area. Histopathology is generally needed to make a definite diagnosis. Available non-invasive imaging techniques in dermatology show opportunities to assist diagnosis of this skin disease. Dermatoscopic features of CCP have been reported by Leerunyakul et al. [2]. Reflectance confocal microscopy (RCM) enables capture of cellular-resolution images of lesions, parallel to the skin surface, at different depths from the stratum corneum to the superficial dermis in vivo, which is a promising imaging tool for the histological evaluation of skin structures in vivo. It has been extensively studied for use in evaluation of cutaneous neoplasms to decrease the biopsy of benign lesions [3]. However, to our knowledge, the RCM findings of CCP have not been previously described in the literature. Herein, we report the RCM features and their histological correlations in CCP.
A 28-month-old girl presented with a 6-month history of asymptomatic hypopigmented papules on the abdomen and pubic skin (Figure 1). The lesions had been increasing in number over time. There was no history of prior rash or trauma in the area. She was otherwise healthy without any pertinent medical or family history. The lesions were given no treatment before she was referred to the dermatology department. On examination there were multiple 2–3 mm, fat-topped, oval hypopigmented papules on the abdomen and pubic skin, which appeared to cluster around the milk lines. Some papules showed a tendency to coalesce. On reflectance confocal microscopy, we discovered the appearance of singly round target shaped cells almost two times larger than the neighbouring keratinocytes near the basal layer of the epidermis (Figure 2 A). Histopathologic examination reviewed a proliferation of oval to round cells with abundant clear cytoplasm arranged singly along the basal cell layer of the epidermis (Figure 2 B), which corresponded to the reflectance confocal microscopy. By immunohistochemistry, these clear cells were positive for CEA, EMA and CK7, but negative for Melan-A and...


View full text...