title: Partial  tetrasomy 9(9pter to 9q2101) due to an extra iso-dicentric chromosome.
abstract: A 3-year-old boy with partial No. 9 tetrasomy is described. The patient showed markedly retarded physical and mental development as well as multiple congenital anomalies. Routine chromosome analysis revealed an extra C-group chromosome. It had a pronounced secondary constriction at the proximal part of its long arm. Based on studies by a variety of banding techniques, the extra chromosome was identified to be an iso-dicentric No. 9 chromosome with inactivation of one of the two centromeres, the karyotype being 47,XY, + DIC (9)(Q2101). The value of BrdUrd treatment was emphasized in the detection of a very small piece of euchromatin within a long stretch of constitutive heterochromatin.
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D002869:Chromosome Aberrations; D002906:Chromosomes, Human, 6-12 and X; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male