Uniparental maternal disomy 6 in a renal transplant patient.

HLA analysis of the family of a renal transplant patient revealed an extremely rare condition. On repeated typings the only demonstrable HLA antigens shown in the propositus were from the maternal haplotype, HLA-A11,-B46,-CW1,-DR14,-DQ1. No paternal antigens could be demonstrated either by serologic or by DNA-typing methods. A paternity investigation was carried out to exclude the possibility of the legal father not being the biological father. The results of this investigation showed a paternity index I = > 20000 and a fatherhood probability W = > 99.995%. Karyotyping of the patient showed two normal chromosomes 6 and no other chromosomal abnormalities. Maternal isodisomy was demonstrated from the analysis of polymorphic DNA markers, involving the short as well as the long arm of chromosome 6. These data are consistent with this patient having the first uniparental maternal disomy 6 reported (inheritance of two identical chromosome 6 haplotypes from the mother and none from the father).