Pallister—Killian syndrome [i(12p)]: first pre-natal diagnosis using cordocentesis in the second trimester confirmed by in situ hybridization

Pallister–Killian syndrome (PKS) is the most frequent form of partial autosomal tetrasomy 12p in humans. Sufferers have a mosaic of isochromosome 12p [i(12p)]. We report the first pre-natal diagnosis on fetal blood cells after cordocentesis during the second trimester. The extra chromosome was first diagnosed by in situ hybridization. Fluorescence in situ hybridization (FISH) was used to count the interphase and/or metaphase cells containing the isochromosome. A review of the literature identified 27 other reports of PKS diagnosed pre-natally. We showed that the most consistent pre-natal ultrasound findings include hypertelorism, broad neck, shorts limbs, abnormal hands or feet, diaphragmatic hernia and hydramnios. Recognition of this congenital malformation pattern pre-natally may allow utilization of FISH.