The cause of Poland anomaly is uncertain. However, it is thought that many of the symptoms described in Poland anomaly may result from interrupted blood flow in the developing fetus. The current theory is that during about the sixth week of fetal development, irregular rib growth may block the flow of blood through the subclavian artery. The subclavian artery is a major blood vessel that supplies blood to the head and arms. The severity of this blockage may determine symptom development.

There is a left and a right subclavian artery in humans. The left subclavian artery goes to the aorta, the largest artery in the human body. A blocked left subclavian artery is more likely to result in miscarriage. This could be a factor in why the right side of the body, which receives blood from the right subclavian artery, is two to three times more likely to be affected by Poland anomaly.

General: Due to the usually mild symptoms of Poland anomaly, patients may not be diagnosed until they require cosmetic or reconstructive surgery.

Blood tests: A blood test and examination of the lymph nodes should be performed to test for associated leukemia and non-Hodgkin lymphoma.

Imaging: A chest X-ray can determine rib abnormalities or diaphragm problems. Chest wall abnormalities may require a computed tomography (CT) scan, which uses X-rays to make detailed images of structures inside the body.

General: Symptoms may vary from patient to patient. However, the end of the main chest muscle that normally attaches to the breastbone is always absent.

Common symptoms: Chest deformity and breast asymmetry are usually present, with only one side of the body being affected. The right side of the body is more likely to be affected than the left. The rib cage may be deformed and ribs may be missing. The upper arm, forearm, and fingers may be shortened, which is called brachysymphalangism. Fingers may be missing, misshapen, or fused.

The skin near the affected areas is usually very thin. There may also be a local deficiency of fat under the skin and missing axillary (armpit) hair. On the affected side, the nipple is often smaller and higher than normal in both males and females. In females, the breast tends to be underdeveloped (breast hypoplasia). Lung problems and abnormal shoulder blade formation may also occur.

Other: Less common symptoms include digestive problems, the heart not being centered, diaphragm defects, liver abnormalities, maternal diabetes, underdeveloped kidneys, protrusion of brain tissue, smaller circumference of the head, and abnormally shaped vertebrae or bones of the spine. Poland anomaly has been associated with an increased risk of developing leukemia or non-Hodgkin lymphoma.

Some cases of Poland anomaly have been associated with leukemia and cancer. An oncologist should be consulted following diagnosis.

Severely malformed fingers and arms may cause cosmetic problems. Kidney problems may occur, resulting in kidney failure. Scoliosis (curved spine) may result from abnormally formed vertebrae (bones of the spine). Premature ovarian failure has been observed in rare cases.

Poland anomaly occurs randomly and is usually not inherited. However, there are rare reports of family members and twins with Poland anomaly, suggesting that inheritance may be possible.

The severity of Poland anomaly differs from person to person and is often not diagnosed or reported, which makes the exact incidence difficult to determine. Current estimates are between one in 10,000 and one in 100,000 births.