RESUMO
Poland syndrome, also known as pectoral aplasia-dysdactylia syndrome, is a rare anomaly, characterized by aplasia of the pectoralis major muscle with ipsilateral upper extremity anomalies. The cause of Poland syndrome is still unknown. Several twin patients were reported to propose a genetic or nongenetic hypothesis. We experienced a female baby showing absence of the pectoralis major muscle in a pair of mixed twin. The patient was referred to our hospital for evaluation of an asymmetric chest wall. She showed depression of the left chest wall, ipsilateral nipple hypoplasia, and axillary webbing. A chest CT scan showed aplasia of the left large pectoral muscle. Our patient had no abnormalities such as symbrachydactyly in an ipsilateral upper extremity. In comparison, a physical examination showed that the fraternal twin boy was completely normal.