Multibranched chromosomes 1, 9, and 16 in a patient with combined IgA and IgE deficiency.

Instability of the centromeric region of chromosome 1 and multibranched configurations formed by different numbers and combinations of arms of chromosomes 1, 9, and 16 were found in cultured lymphocytes of a 12-year-old male with combined IgA and IgE deficiency. No chromosome abnormalities were found in fibroblast cultures from the patient or in blood cultures from his parents. A possible effect on the frequency of the abnormalities of the almost continuous antibiotic treatment received by the patient was found both in vivo and in vitro, but no abnormalities were found in blood cultures from control subjects who received similar treatment. Interphase association of chromosomes 1, 9, and 16 and a high frequency of interchanges among the centromeric regions of these chromosomes due to the presence of a fragile site is assumed to be the cause of the abnormalities.