[Two cases of infantile subungual pigmented nevi with Hutchinson's sign]

Two cases of subungual pigmented nevi with periungual melanotic freckles, namely Hutchinson's sign, are presented. They are a 4-year-old female and a 11-month-old male; in neither case did the mother notice the lesion at birth. Histologically, both cases were characterized by the presence of well-circumscribed small nests of nevus cells in the periungual melanotic areas; diagnoses of junctional nevus and compound nevus were made, respectively. However, atypical proliferations of melanocytes at the dermo-epidermal junction of the nail matrix and nail bed were observed in some areas. The measurement of the DNA content of melanocytes by means of microfluorometry revealed normal diploid pattern in the former case, but the latter case contained a few aneuploid cells, suggesting that the proliferating melanocytes might have malignant potentials. Infantile subungual pigmented nevi with Hutchinson's sign must be examined thoroughly and watched carefully.