The Pallister-Killian syndrome in a child with rare karyotype--a diagnostic problem.

The Pallister-Killian syndrome is a clinically recognizable syndrome, usually due to a tissue-specific mosaicism for a 12p isochromosome [i(12p)]. We report a rare case of Pallister-Killian syndrome with 12p mosaicism, tetrasomy/trisomy/disomy in fibroblasts and trisomy/disomy in lymphocytes. Marker chromosomes were investigated with conventional cytogenetic techniques and fluorescent in situ hybridisation (FISH). The karyotype was established as: mos47,XX,+12p/47,XX,+i(12p)/46,XX. The cytogenetic result of the extra mosaic 12p presented in lymphocytes suggested the diagnosis of trisomy 12p, although, in combination with clinical manifestations, the Pallister-Killian syndrome was considered and confirmed by the cytogenetic analysis of fibroblasts.