TETRASOMY 12P (PALLISTER-KILLIAN SYNDROME) - ULTRASOUND INDICATORS AND CONFIRMATION BY INTERPHASE FISH

Tetrasomy 12p (Pallister-Killian syndrome) is a mosaic aneuploidy synd rome in which the isochromosome is present in amniocytes with a much g reater percentage than fetal lymphocytes. Two new cases identified by prenatal diagnosis are reported. Indications for prenatal diagnosis we re advanced maternal age and fetal anomalies. The most consistent repo rted prenatal ultrasound findings for tetrasomy 12p include polyhydram nios with short femurs and a diaphragmatic hernia. Recognition of cong enital malformation patterns prenatally may allow appropriate selectio n of tissue for chromosome analysis. Molecular cytogenetic analysis us ing fluorescence in situ hybridization was used retrospectively to con firm the presence of the isochromosome 12p in various formalin-fixed f etal tissues. The levels of mosaicism detected in fetal and placental tissues were lower than those detected prenatally.