Identical multiple congenital anomalies/mental retardation (MCA/MR) syndrome due to del(2)(q32) in two sisters with intrachromosomal insertional translocation in their father.

We report two sisters with a deficiency of band 2q32 that resulted from meiotic crossover events in their father, who is a balanced, intrachromosomal insertional translocation heterozygote. This three-break rearrangement involving a single chromosome is among the rarest class of human structural chromosome abnormalities. A review confirms the theoretically predicted high risk of unbalanced progeny for such translocation heterozygotes. Fertility of carriers seems to be unimpaired in either sex. Available information is insufficient to define the effect of insertional translocation on homologue pairing, crossover frequency, and other meiotic phenomena.