Multi-dermatomal unilateral nevus comedonicus along the lines of Blaschko: a rare presentation

Abstract

Nevus comedonicus is a rare skin disorder due to defect in development of hair follicle presenting as groups of closely set, dilated follicular openings with dark keratin plugs resembling comedones. The lesions may be distributed in a linear, interrupted, unilateral or bilateral pattern and sometimes follow the lines of Blaschko. It may develop inflammatory acne-like lesions leading to cysts, abscesses and scarring. A 36 year-old woman presented with multiple pits on left half of the body involving the face, upper limb, shoulder, back and buttock since the age of 4 years. She also had a painful swelling over the back. There was no history of cranial, skeletal or ocular involvement. Physical examination revealed multiple circular honeycomb-type pitted scars sized from 0.1×0.1 to 0.5×0.5 mm present unilaterally along lines of Blaschko in an interrupted pattern over the left half of the body as mentioned above. Among these pitted scars few scattered comedones were present with interfollicular normal skin. There was an abscess along the margin of one of the lesions over the back which was tender, indurated and with local rise of temperature. Histopathological examination revealed deep, wide invagination of acanthotic epidermis, filled with concentric lamellae of keratin. Hair shafts were occasionally seen in the dermis, below the lower part of invagination. Based on clinical and histopathological picture a diagnosis of nevus comedonicus was made. She was treated with topical tretinoin and oral retinoids without much improvement. Nevus comedonicus in itself is a rare epidermal nevus, its multi-dermatomal unilateral distribution along the lines of Blaschko is even rarer.