Tetrasomy 12p presenting with long appendix: a prenatal case.

Pallister-Killian Syndrome (PKS) is a rare multi-system condition caused by mosaicism for tetrasomy of chromosome 12p (3). PKS is characterized by the presence of a supernumerary isochromosome composed of the short arms of chromosome 12, resulting in tetrasomy 12p. The condition is often present in a tissue limited mosaicism; skin fibroblasts have 47 chromosomes with an extra small metacentric chromosome, whereas the karyotype of blood lymphocytes is normal. The PKS phenotype has also often been observed in individuals with complete or partial duplications of 12p region (2,4,5). Approximately 200 cases with PKS have been reported until now (6).We report ultrasonographic and pathologic features of a case of tetrasomy 12p diagnosed prenatally. The mother was referred to our genetics department because of advanced maternal age at 17 weeks of pregnancy. She was 44-years-old with gravida 5, parity 3, abortus 1. The family history was unremarkable and the parents were unrelated. A detailed ultrasound scan of the fetus revealed a single fetus with biparietal diameter of 31 mm, head circumference of 117 mm, femur length of 17 mm (Prenatal diagnosis was recommended and with the parents consents amniocentesis was performed. Cytogenetic analysis of amniotic fluid revealed a male karyotype with a supernumerary chromosome consistent with an isochromosome 12p. The genotype was unbalanced by the presence of a tetrasomy of the short arm of the chromosome 12. After targeted FISH with arm-specific probe for chromosome 12, tetrasomy 12p was confirmed. We diagnosed the fetus as PKS.After the results of fetal karyotyping at 23rd weeks of pregnancy, detailed doppler ultrasound scan revealed lack of fetal movements, brachydactyly with broad halluxes, abnormal appearance of the hands and feet with facial dysmorphism that included a coarse face with hypertelorism, frontal bossing, prominent metopic suture, flat fetal face, pre-frontal edema (7mm), short nose, micrognathia, low-set ears, and polyhydramnios. After the cytogenetic results and genetic counseling, the pregnancy was terminated with the consent of the parents.Inspection and autopsy of the fetus revealed a male fetus consistent with 23 weeks of age with marked typical face for PKS. Facial dysmorfism was noted with hypertelorism, sparse eyebrows, a wide and flat nasal bridge, epicanthus, frill cheeks, a simple and long philtrum, low set and dysplastic ears, short nose, anteverted nares, thick lower lip and micrognathia. Palate was high and narrow. The neck was short and mildly webbed with excess of nuchal fold. The nipples were widely spaced. There were bilateral brachydactyly with broad halluxes in the hands. …