Congenital Smooth Muscle Hamartoma: a Patchy Follicular Variant

Cutaneous smooth muscle hamartomas are benign proliferations of smooth muscle bundles within the dermis. They can be congenital or acquired, and most cases are congenital. Congenital smooth muscle hamartomas (CSMHs) usually manifest at birth as well-circumscribed, frequently hypertrichotic, hyperpigmented or skin-colored patches or plaques on trunk or extremities.

We report a case of CSMH in a 10 year-old girl, who showed a localized skin-colored patch showing prominent follicular papules on the lateral aspect of her right upper arm, which were found at birth. There was no hypertrichosis and the pseudo-Darier sign was negative. This patchy follicular variant is the less common clinical type of the disease.