Congenital panfollicular nevus associated with polydactyly.

A 2-year-old girl presented with ulnar-sided duplication of the left thumb distal to the interphalangeal joint and syndactyly of the first web space. She also had several asymptomatic pink-tan cutaneous papules, involving the first and second ray of the left hand and wrist, clinically resembling a linear epidermal nevus. Microscopically, the papules were composed of well-circumscribed aggregates of basaloid epithelium within the dermis. No normal hair follicles were identified. Follicular germ and papillae were identified, representing abortive attempts at hair follicle formation. The features were remarkably similar to a novel entity described by Finn and Argenyi as congenital panfollicular nevus. In our case, the congenital panfollicular nevus was associated with distal thumb polysyndactyly, which may suggest an important link between limb patterning and hair follicle development.