Deletion in the ABL gene resulting from a meiotic recombination of a maternal (3;22;9)(q22;q12;q34.1) translocation.

Complex chromosome translocations involve changes between three or more chromosomes and are found very rarely in the general population. 2 Abnormal phenotype, mental retardation, recurrent miscarriages, and infertility have been reported in carriers of apparently balanced complex chromosomal rearrangements. Phenotypic abnormalities in patients with apparently balanced chromosomal translocation could be the result of several mechanisms. A breakpoint in one derivative chromosome may have occurred within a gene leading to loss of gene function. In other cases, an abnormal phenotype could be the result of genomic imprinting, as observed in translocations involving chromosomes 11 or 15. 6 Another explanation is the possibility of cryptic rearrangements such as deletion or duplication of chromosomal segments near the breakpoints. By using conventional cytogenetic techniques, these balanced chromosomal translocations have no apparent loss or gain of genetic material. However, the characterisation of subtle chromosome anomalies in chromosomal translocations is difficult because of the resolution limit of banding analysis. The use of fluorescence in situ hybridisation (FISH) has greatly improved the accuracy of cytogenetic diagnosis and uncovered a number of cryptic chromosomal anomalies. We report an inherited, apparently balanced complex translocation in a child with axial hypotonia and dysmorphism.