Congenital Partial Absence of the Pectoralis Major Muscle

A 22-year-old man's chest shows the most common form of congenital pectoralis major muscle anomaly-partial absence of the right pectoralis major muscle with the clavicular origin intact.

The abnormality was noted during a routine preemployment physical examination. There was no apparent decrease in shoulder internal rotation or adduction strength, and the patient had not noticed any shoulder weakness or limitation in motion. Partial or complete absence of the pectoralis major muscle usually is reported in Poland's syndrome, with associated ipsilateral upper extremity anomalies such as syndactyly. A reduction in shoulder strength may occur, but significant loss of function is unlikely.