PALLISTER-KILLIAN-SYNDROME - NORMAL KARYOTYPE IN PRENATAL CHORIONIC VILLI, IN POSTNATAL LYMPHOCYTES, AND IN SLOWLY GROWING EPIDERMAL-CELLS,BUT MOSAIC TETRASOMY-12P IN SKIN FIBROBLASTS

We report on two patients with Pallister-Killian syndrome: an 18 month old male infant followed since the neonatal period and a 4 year old b oy. Prenatal diagnosis by chorionic villi sampling (CVS) in the first case showed a normal karyotype without mosaicism. Chromosome analysis on peripheral lymphocytes of the newborn also showed a normal karyotyp e. The clinical diagnosis of Pallister-Killian syndrome was made after the first year of life because of he typical facial dysmorphism and o ther characteristic clinical features, such as frontotemporal alopecia , depigmented area of the skin, sensorineural hearing loss, and severe psychomotor retardation. Chromosome analysis from skin fibroblasts no w showed an isochromosome 12p mosaicism. The origin of the extra chrom osome was confirmed by in situ hybridisation using a chromosome 12 spe cific library. In the second case chromosomal analysis from peripheral lymphocytes at the age of 19 months showed a normal karyotype 46,XY. Following the clinical diagnosis of Pallister-Killian syndrome a super ficial skin biopsy was performed which showed very poor and slow growt h of cells and a normal karyotype. Because of the typical symptoms a l arger and deeper skin biopsy was performed from which there was rapid growth of fibroblasts. Now the diagnosis was established on the basis of the presence of an i(12p) extra chromosome in 69% of the metaphases .