Abdominal wall defects distant from the umbilicus are very unusual. We describe a patient with a congenital defect adjacent and external to the lateral border of the recti muscles, rounded in shape, bilateral and symmetrical, but affecting different structures in each side, musculocutaneous agenesis in the left side and only muscle agenesis in the right one. The morphologic characteristics of the defect and the absence of associated anomalies, suggest that this anomaly may be the result of an event acting during phenogenesis. We consider that this defect is different from other structural abnormalities of the anterior abdominal wall which occur much earlier at certain periods of the embryogenesis. Though the etiology is speculative, we could postulate a disruptive origin of the defect of unknown cause.