The severity and extent of abnormalities varies between individuals, and it is rare to have all the features of Poland syndrome. There is hypoplasia (underdevelopment) of the ribs and chest wall. The most common abnormality of the shoulder girdle and chest wall is absence of part of the chest muscle (known as the pectoralis major) which makes the anterior (front) fold of the armpit. In girls, this may be associated with undergrowth or complete absence of a breast, and a small or absent nipple and areola (pink or brown circle around the nipple). There may also be absence (agenesis) or hypoplasia of other chest muscles (including the pectoralis minor).
The affected arm may be underdeveloped. Abnormalities of the hand vary from a mild change in skin crease patterns to complete absence of some fingers, and the hand is often small. In some cases, the skin and sometimes the bone has not separated during development and is still joined together (this is known as syndactyly). Brachydactyly (short fingers) can also occur.