Congenital unilateral hypoplasia of depressor anguli oris muscle in adult.

Congenital hypoplasia of the depressor anguli oris muscle is a rare cause of asymmetrical crying facies in newborns. The clinical manifestations range from mild to severe asymmetry and may persist up to adulthood. In the current case, the patient did not exhibit other congenital anomalies or paralysis of other branches of the facial nerve. This adult patient presented with severe asymmetrical lower lip deformity during full mouth opening since birth. A chromosomal study for the detection of 22q gene deletion yielded negative results. The electromyography findings of the lower lip were insignificant. Depressor labii inferioris muscle resection was not effective, but bidirectional (horizontal and vertical) fascia lata grafting improved the aesthetic appearance of the asymmetrical lower lip. The patient showed improved lower lip symmetry during full mouth opening at 1 year after the surgery. Therefore, the details of this rare case are reported herein.