Congenital dermal sinus tract in the lateral buttock: unusual presentation of a typically midline lesion.

Congenital dermal sinus tracts most commonly involve the midline and may communicate with the central nervous system. We present a 3-year-old girl with a pit in the upper lateral buttock noted since birth. Surgical exploration revealed a firm tract that dissipated in the gluteal fascia, and ultrasound confirmed the absence of any deeper extension. Microscopic examination revealed a sinus tract lined by dermal appendages and surrounded by an exuberant inflammatory reaction to hair. This location is distinctly unusual, and our report expands the clinical spectrum of congenital dermal sinus tracts and raises awareness that lesions prone to having a connection with the central nervous system may present quite laterally. Furthermore, this case provides insight into the pathogenesis of a disease that is often explained as a "defect of midline closure" and also illustrates an unusual setting for so-called "pilonidal disease."