Habitual abortion and translocation (22q;22q): unexpected transmission from a mother to her phenotypically normal daughter

This paper describes the unexpected transmission of a translocation (22;22) (pl3;qll) from a mother to her phenotypically normal daughter (the proband). Both women had had multiple abortions. No signs of mosaicism with respect to chromosome No. 22 were found in the proband or in her mother. Until now, it has been generally assumed that carriers of a 22/22 translocation will have only abnormal conceptuses. The transmission of this translocation from a balanced carrier to a phenotypically normal daughter was therefore highly unexpected and is not easy to explain. Early postzygotic loss of a chromosome no. 22 from a trisomic zygote, or fertilization of an oocyte carrying the translocation by a sperm nullisomic for chromosome no. 22 could have led to the balanced chromosome pattern of the proband.