Clinical, cytogenetic, and molecular observations in a patient with Pallister‐Killian‐syndrome with an unusual karyotype

Pallister‐Killian syndrome is a clinically recognizable syndrome, usually due to a tissue‐limited mosaicism for a supernumary 12p isochromosome (i12p). Here we report an unusual case with tetrasomy/trisomy/disomy 12p mosaic in fibroblasts and trisomy/disomy 12p mosaic in lymphocytes. The tetrasomy 12p was due to an i12p, the trisomy 12p to a single 12p marker. Both marker chromosomes were investigated with conventional cytogenetic techniques and fluorescent in situ hybridization (FISH). Stability under culturing conditions was studied. DNA‐analysis revealed prezygotic maternal origin of the extra 12p material. Clinically, the patient seems to have less retardation than most patients with Pallister‐Killian syndrome. © 2003 Wiley‐Liss, Inc.