Is Pallister-Killian mosaic syndrome inherited ?
Pallister-Killian mosaic syndrome is not inherited. The chromosomal change responsible for the disorder typically occurs as a random event during the formation of reproductive cells (eggs or sperm) in a parent of the affected individual, usually the mother. Affected individuals have no history of the disorder in their families.  An error in cell division called nondisjunction likely results in a reproductive cell containing an isochromosome 12p. If this atypical reproductive cell contributes to the genetic makeup of a child, the child will have two normal copies of chromosome 12 along with an isochromosome 12p.  As cells divide during early development, some cells lose the isochromosome 12p, while other cells retain the abnormal chromosome. This situation is called mosaicism. Almost all cases of Pallister-Killian mosaic syndrome are caused by mosaicism for an isochromosome 12p. If all of the body's cells contained the isochromosome, the resulting syndrome would probably not be compatible with life.