Balanced chromosome translocations and abnormal phenotypes. A report of 5 cases

Five cases in which phenotypic abnormalities were found in association with apparent balanced chromosomal translocations are described. In 3 patients, one of the parents was found to be a carrier of the same translocation. In a further patient, the translocation was shown to be de novo and in the remaining patient the father was not available for chromosome studies. In a review of the literature the breakpoints in 36 familial balanced translocations were compared with 40 de novo translocations (including the present cases) all associated with phenotypic abnormalities. No common translocation was found in these groups, but it was observed that chromosomes 4 and 5 were significantly more involved in de novo translocations than in familial translocations. The possible aetiology and implications for prenatal diagnoses are discussed.