BETA-THALASSEMIA IN INDIGENOUS BELGIANS - AN UPDATE

Beta-thalassaemia, a widespread autosomal recessive disorder, occurs s poradically in Northern and Western European countries. Molecular anal ysis of ths beta-globin gene has been carried out in 30 members of 15 unrelated indigenous Belgian families which presented with non siderop enic hypochromic and microcytic anaemia. For all of them, extensive se arch failed to find an ancestor at risk for the disease. The beta-glob in genes were first screened for frequent beta-thalassemic mutations b y dot-blot hybridization with specific radiolabeled oligonucleotide pr obes. Direct automated fluorescence-based DNA sequencing and, in one c ase, Southern blotting were also used. All the 30 patients were found to be heterozygous fora beta-thalassemic mutation, Eight different mut ations were identified. Among these, four are commonly found in the Me diterraneans: codon 8 (-AA), IVS-I-l (G-->A), IVS-1-6 (T-->C) and codo n 39 (C-->T); three have occasionnaly been reported: initiation codon (T-->C) and codon 35 (C-->A) and a rare deletion of 12.6 kb which remo ves all the beta-globin gene and its flanking regions. A new mutation, a -CC deletion at codon 38/39 was found in one family. These results both at the biological and molecular level show that beta-thalassaemia exist in indigenous Belgian families with no known ancestor a risk fo r the disease. They also show that clinicians and biologists should ke ep in mind the existence of beta-thalassaemia in indigenous Belgian fa milies when investigating hypochromic and microcytic anaemia in patien ts whom the past familial history does not evocate a risk for the dise ase.