Mucosal-lined hemiperineal anomaly possibly caused by antenatal rupture of a caudal duplication.

In a 1-month-old infant with a mucosal-line left hemiperineal defect associated with penoscrotal hypospadias, penoscrotal transposition (PST) and an overhanging caudal skin-covered soft-tissue flap resembling a caudal appendage, perineal anatomy could be restored by excising the mucosa and using the overhanging flap to cover the resultant defect. The PST was corrected at the same time. Squamous, gastric, small-intestinal, and respiratory epithelia were present histologically in the mucosa in addition to adjacent cartilaginous elements. A caudal duplication that had ruptured in utero through the hemiperineum could explain the anomaly.