Congenital smooth muscle hamartoma on the scalp.

An 8-day-old male infant was referred to our neonatal unit for prematurity. It was observed that his scalp color was darker than the rest of his skin color when the scalp hair was partially shaved for intravenous access. Dermatologic examination revealed a slightly elevated, hyperpigmented plaque confined to the whole scalp. The margin of the lesion did not extend to the face and neck. His hair was abundant and dark (Fig. 1). There were no areas of alopecia and no overlying folds of skin. There were no dysmorphic features, such as Michelin tire baby. Pseudo-Darier’s sign was negative. A punch biopsy specimen was obtained from the lesion with a diagnosis of congenital melanocytic nevus or congenital blue nevus. The result of histopathologic examination showed increased smooth muscle bundles in the reticular dermis running in various directions under a normal epidermis (Fig. 2a); immunohistochemical stain revealed desminpositive (Fig. 2b) and S100-negative proliferation. Based on these clinical and histopathologic findings, a diagnosis of congenital smooth muscle hamartoma was made. No changes in this lesion were observed during a 9-month follow-up period.