Poland syndrome is a birth defect characterized by an underdeveloped chest muscle and short webbed fingers on one side of the body. There may also be short ribs, less fat, and breast and nipple abnormalities on the same side of the body. Typically, the right side is involved. Those affected generally have normal movement and health. The cause of Poland syndrome is unknown. One theory is that it is due to disruption of blood flow during embryonic development. It is generally not inherited, and no genes that contribute to the disorder have been identified. Diagnosis of Poland syndrome is based on its symptoms. Often, those with the syndrome remain undiagnosed, and some may not realize they have it until puberty. Treatment of Poland syndrome depends on its severity and may include surgical correction. The syndrome affects about 1 in 20,000 newborns, and males are affected twice as often as females. It is named after English surgeon Sir Alfred Poland, who described the condition when he was a student in 1841. Signs and symptoms A list of the common side effects broken down by frequency. Very frequent Abnormal gastrointestinal tract Absent pectoral muscles Brachydactyly (Short fingers) Dextrocardia Diaphragmatic hernia/defect Humerus absent/abnormal Liver/biliary tract anomalies Maternal diabetes Oligodactyly/missing fingers Radius absent/abnormal Rhizomelic micromelia (relatively shorter proximal segment of the limbs compared to the middle and the distal segments) Sparsity or abnormality of axillary hair on affected side Syndactyly of fingers (webbing) Ulna absent/abnormal Upper limb asymmetry Abnormal rib Simian crease on affected side Frequent Hypoplastic/absent nipples Scapula anomaly Occasional Agenesis/hypoplasia of kidneys Encephalocele/exencephaly Abnormal morphology of hypothalamic-hypophyseal axis Abnormal function of hypothalamic-hypophyseal axis Microcephaly Preaxial polydactyly Ureteric anomalies (reflux/duplex system) Vertebral segmentation anomaly It is usually considered a unilateral condition. Some have claimed that the term can be applied in bilateral presentation, but others recommend using alternate terminology in those cases. Causes The cause of Poland syndrome is unknown. However, an interruption of the embryonic blood supply to the arteries that lie under the collarbone (subclavian arteries) at about the 46th day of embryonic development is the prevailing theory. The subclavian arteries normally supply blood to embryonic tissues that give rise to the chest wall and hand. Variations in the site and extent of the disruption may explain the range of signs and symptoms that occur in Poland syndrome. Abnormality of an embryonic structure called the apical ectodermal ridge, which helps direct