Background:

Dermal melanocytosis is a group of pigmentary dermatological diseases associated with melanocytic proliferation, which are classified based on their number and depth at the level of the dermis; they may be congenital or acquired.

Case report:

An 11-year-old male patient with no history of importance for the current condition started 5 years ago with a dark macula in the left hand palm, which was asymptomatic but grew gradually. On physical examination, dermatoses affecting the left palm, palmar face of proximal phalanges of the third, fourth and fifth fingers, characterized by the presence of blackish greyish macula, diffuse and irregular edges, not infiltrated or indurated were detected. The dermatoscopy identified a pattern of pigment with a greyish-brown tone with brown areas, showing whitish spots inside. In the histopathology, the presence of spindle cells was observed in the superficial and middle dermis, with a large nucleus and the presence of a melanic pigment inside, with perivascular distribution and intermingled with the collagen fibres. Based on the clinical characteristics and the histopathological findings, acquired dermal melanocytosis of the hand was concluded as the final diagnosis.

Conclusions:

Case reports of atypical acquired dermal melanocytosis are infrequent. Dermal melanocytosis of the hand is a rare variant of these diseases, of which less than 10 cases have been reported. At present, this case of dermal melanocytosis is the first reported in Latin America with the aim to extend the knowledge of its clinical-histological and dermatoscopic characteristics.