Pallister-Killian syndrome

Pallister-Killian syndrome, abbreviated PKS, is also called tetrasomy 12p mosaicism or the Pallister mosaic aneuploidy syndrome. The source lead calls it an extremely rare and severe genetic disorder. It arises from an extra, abnormal small supernumerary marker chromosome that carries multiple copies of the short arm of chromosome 12; together with the two normal copies, these extra copies are overexpressed and cause the syndrome. Because of genetic mosaicism, the marker chromosome is distributed differently between tissues, so affected people differ in their birth defects and severity. The lead gives the example that a person with the marker in heart tissue is likely to have structural heart abnormalities, while one without it there has a structurally normal heart. This entry is a record of the condition, not medical advice.