[Beta thalassemia in Germany: molecular genetics and clinical phenotype in immigrant and in the native population].

BACKGROUND In Germany there are about 300-400 patients with homozygous beta-thalassaemia who immigrated from endemic regions mostly in the Mediterranean. In the non-immigrant population beta-thalassaemia is rare with only single case reports of homozygous patients. Heterozygous beta-thalassaemia, however, is more common and must be considered in the differential diagnosis of hypochromic anemia. PATIENTS AND METHODS Here, clinical and molecular data of 221 homozygous patients from immigrant families and 256 non-immigrant German heterozygous individuals are presented. RESULTS Clinically, 87% (n = 192) of the homozygotes are regularly transfused and classified as thalassaemia major (TM). The other 13% (n = 29) are not (regularly) transfused and thus classified as thalassaemia intermedia (TI). There is a wide spectrum of 39 beta-globin gene mutations and even the most common three, IVSI-110G-A, NS 39, and IVSI-6 T-C occur with relatively low frequencies of 28%, 22%, and 9%, respectively. In 17/29 (58%) TI patients "mild" mutations are found that inactivate the affected gene incompletely. In 16/29 (55%) there are mutations that are associated with increased gamma-globin gene activity. alpha-Thalassaemia is rare and only found in 3/29 TI-patients. In the 256 Germans with heterozygous beta-thalassaemia there are 27 different beta-globin gene mutations. The 3 most common are Mediterranean mutations together accounting for 61%. Also-relatively common (5%; n = 13) is an otherwise rare frameshift mutation of codon 83 (FS83 delta G). The other mutations occur in < 10 individuals only. Two mutations described here are novel. One of them affects position-2 of the intron 1 splice acceptor site (IVSI-129 A-G) and the other is a deletion of a single G in codon 15/16 (FS 15/16 delta G). CONCLUSIONS Taken together, a plausible molecular pathogenesis for the observed phenotype (TM vs. TI) can be identified in most homozygous patients thus allowing for rational counselling of the affected families. In heterozygous Germans beta-thalassaemia has probably been imported from the Mediterranean in about 2/3 of the cases whereas in the remaining 1/3 it has probably originated locally.