NEW RFLP MARKER, SP282, AT THE BTK LOCUS FOR GENETIC-ANALYSIS IN X-LINKED AGAMMAGLOBULINEMIA FAMILIES

X-linked agammaglobulinaemia is an inherited recessive disease in whic h the primary defect lies in the failure of pre-B cells to develop int o mature circulating B cells, due to a defective B-cell cytoplasmic ty rosine kinase (btk). For this study we introduced a new RFLP marker, S P282, which is tightly linked to the XLA locus. In conjunction with th e marker DXS178, SP282 was used to identify a carrier female and predi ct her male offspring to be normal. Subsequently the fetus was shown t o have a normal number of circulating B cells, and at 2.5 years of age , the non-affected phenotype of the child was confirmed.