[Homozygote beta-thalassemia in 2 Dutch families].

beta-thalassaemia is a haematological disorder which is rare in The Netherlands although the influx of carriers from Mediterranean, West Indian, and South American countries has increased its frequency. Only a few homozygotes have been found among the original Dutch population. In this article, we describe the molecular abnormality observed in two such homozygotes. Both patients were mildly affected and had the same C-G mutation in the beta-globin gene promoter at position -87 relative to the Cap site of the beta gene. This mutation is known to cause a mild beta +-thalassaemia. Additional studies of the epsilon-gamma-delta-beta-globin gene complex on chromosome II, i.e. haplotype analyses, identified three different haplotypes in the two patients. However, crossovers might have been responsible for these differences because the 3' haplotype, which involves restriction sites within and 3' to the beta-globin gene, was the same for all four chromosomes in the two homozygotes.