Molecular and Cytogenetic Characterization of a Fetus with Mosaic Ring Chromosome 13: A Very Rare Case

The major mechanism for ring chromosome formation is thought to result from breakage and reunion at the breakpoints on the long and short arms of a chromosome. This fusion event can produce terminal arm inversions, deletions, and duplications that determine the resulting phenotype.[1] Ring chromosome 13 is relatively uncommon, with an estimated incidence of 1/58,000 live births. Clinical severity of ring chromosome 13 syndrome is broad and influenced by the stability of the ring as well as the extent of the deletions and/or duplications along chromosome 13.[2] Prenatal diagnosis of ring chromosome 13 is very rare. Here, we present a prenatal case with molecular cytogenetic characterization of mosaic ring chromosome 13 syndrome in a fetus with multiple abnormal ultrasound findings.