Multiple acquired smooth muscle hamartomas with thick-walled blood vessels on scalp.

Smooth muscle hamartoma (SMH) is a benign hamartomatous condition that consists of a dermal proliferation of smooth muscle cells. We hereby report a case of multiple, acquired SMHs on scalp. A 25-year-old male had a 6-year history of multiple, asymptomatic, hyperpigmented plaques on the scalp which were progressively increasing in number and size. Histopathological examination revealed large thick-walled blood vessels, in addition to the haphazardly arranged discrete smooth muscle bundles in the reticular dermis. This case of SMH is unusual in being acquired, having multiple lesions, involving scalp, and having thick-walled blood vessels apart from arrector pili muscle bundles. It emphasizes the wide spectrum of clinical and histopathological variations that may be associated with acquired SMH.