Class II Analphoid Chromosome in a Child with Aberrant Chromosome 7: A Rare Cytogenetic Association.

A neocentromere is a functional centromere that has arisen within a region not known to have a centromere. We present a case with a very rarely reported class II neocentromere formation in an aberrant chromosome 7. A 22-month-old male was referred because of dysmorphic features. Banding cytogenetics was performed, and a ring 7 and a supernumerary marker chromosome along with a normal chromosome 7 were found. In situ hybridization using a centromeric probe revealed 46 signals, of which 2 signals for chromosome 7 were observed, one on the normal and one on the ring chromosome. Further analysis using FISH revealed that the linear acentric fragment was part of the 7q region, which suggests that there could be a possible McClintock mechanism.