A chromosomal event resulting in possession and expression of multiple HLA-B and Cw genes in a renal patient.

Routine HLA typing of a renal patient for purposes of registration for transplantation revealed an unusual human leucocyte antigen (HLA)-B and Cw genotype, with three specificities detected. Results were confirmed in a second sample, and in a second laboratory. The possibility of these results reflecting a chimaeric state was rejected following short tandem repeat (STR) analysis. Although cytogenetic analysis has failed to detect a chromosomal abnormality, these findings support the view that the aberrant expression of HLA in this patient resulted from an unequal crossover event, occurring during meiosis in a previous generation.