Rhabdomyomatous Mesenchymal Hamartoma With Prominent Folliculosebaceous Hyperplasia in an Infant's Philtrum: A Case...

Rhabdomyomatous mesenchymal hamartoma (RMH) is a rare congenital malformation. We report a case involving a 20-month-old girl who presented with a congenital midline philtral mass. Histopathological examination revealed mature striated muscle fibers interspersed with adipose tissue and prominent adnexal structures, including sebaceous glands originating from hair follicles. The lesion's prominent folliculosebaceous components initially suggested folliculosebaceous cystic hamartoma (FSCH). However, the presence of striated muscle hyperplasia, midline location, congenital onset, and the absence of characteristic cleft formation confirmed the diagnosis of RMH. The patient underwent complete surgical excision and was recurrence-free after 5 years of follow-up. This case highlights the importance of considering RMH in the differential diagnosis of congenital midline facial lesions, including those with adnexal components.