Hutchinson’s Nail Sign – Subungual melanoma

This is an answer to the Case – Black Nail

A 37-year-old man presented with a brownish-black nail on the great toe of the right foot. A darkly pigmented linear patch had started to form within the toenail 4 years earlier and had widened and darkened over time.

Two months before the current presentation, the dark pigment had begun to involve the hyponychium and the proximal and lateral nail folds. The patient’s personal and family medical histories were otherwise unremarkable.

The results on routine laboratory testing were within normal limits. An incisional biopsy of the nail matrix showed atypical melanocytes and inflammatory cells along the basal layer of the epidermis, findings consistent with acral lentiginous melanoma in situ.

Subungual melanoma, a variant of acral lentiginous melanoma, arises from the nail matrix, most commonly in the great toe or thumb. Hutchinson’s nail sign is an important clinical clue to subungual melanoma and is characterized by extension of brown or black pigment from the nail bed, matrix, and nail plate to the adjacent cuticle and proximal or lateral nail folds.

The patient underwent amputation of the great toe, and he remains healthy 8 years later.