Posterior shoulder girdle abnormalities with absence of pectoralis major muscle

We have reviewed 12 consecutively ascertained individuals with unilateral absence of the sterno-costal head of the pectoralis major muscle and have studied associated abnormalities of the posterior shoulder girdle and their frequency and extent as contrasted with that of the symbrachydactyly. We found certain previously unreported associations of skeletal and renal anomalies in these individuals. We review various speculations regarding the possible causes of the Poland anomaly.