[Analysis of a program for atypical familial microcytosis. Molecular basis for alpha-thalassemia. GEHBTA].

The results of a programme for the study of atypical familial microcytosis are analysed in this paper. The techniques used were "in vitro" synthesis of globin chains in tritiated leucine-labelled reticulocytes and genetic mapping with different restriction enzymes, plus the usual haematimetric values. Of the 134 syntheses performed, 73 showed alpha/beta ratio lower than 1 (alpha-thalassaemia). The lowest values, alpha/beta ratio of 0.54 +/- 0.14, corresponded to 3 patients with Hb H disease. In general terms, our findings are similar to those reported in the literature. The genetic mapping was performed in 98 patients with alpha-thalassaemia (73 cases with decreased alpha/beta ratio, 2 cases with normal ratio, and 23 relatives). Of the 98 patients, 3 had Hb H disease, 70 corresponded to heterozygous alpha zero-thalassaemia, 11 to homozygous alpha(+)-thalassaemia, and 14 to heterozygous alpha(+)-thalassaemia. The analysis of DNA revealed the heterogeneity of the molecular alterations, the prevalent haplotypes being (- -MED), in 74% of the patients, and (-3.7 alpha), in 100% of the cases. The other alpha zero-thalassaemia mutations found were the deletions (- -SEA) and (- -SPAN) and the "no-deletion" thalassaemias.