Disomic balanced reciprocal translocation.

The previously unreported and unique finding of a complete disomy of an apparently balanced reciprocal translocation is described. The parents are second cousins once removed and each parent contributed the same balanced reciprocal translocation chromosome. Although the complete disomy involves balanced translocation chromosomes from unaffected parents, it is possible that a hemizygous state of some genes may be present on each translocation chromosome, which in a disomic homozygous state could result in an abnormal phenotype, as manifested by infantile seizures in this patient.