T. Eggermann et al., NEW CASE OF MOSAIC TETRASOMY 9P WITH ADDITIONAL NEUROMETABOLIC FINDINGS, American journal of medical genetics, 75(5), 1998, pp. 530-533
Tetrasomy 9p is a rare chromosomal aberration that was described in 28
previous patients, Here we report on a newborn girl who was referred
for genetic evaluation because of developmental delay, hypertonicity,
microcephaly, minor anomalies, and neurometabolic findings. She had an
isochromosome 9p (pter --> p10 --> pter) in 32% of blood cells, The e
xtra chromosome was not found in amniocytes. Examination of fibroblast
s from different skin biopsies also showed mosaicism in this tissue. I
n a first biopsy from the abdominal wall, the cells (n = 50) had a nor
mal chromosomal complement. Further analysis of fibroblasts from the l
eft forearm showed the isochromosome 9p in 5 out of 8 mitoses, Fluores
cence in situ hybridization (FISH), using a whole chromosome 9 probe,
confirmed that the extra marker was 9 in origin, Molecular studies sho
wed that the isochromosome was of maternal origin. Meiotic nondisjunct
ion was followed by centromeric misdivision and postzygotic loss of-th
e marker.