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We report the study by restriction mapping of alpha genes in a case of Hb H disease in Tunisia. The genotype is: -alpha/-alpha which by itself is not usually responsible for the HbH phenotype. We postulate that the two remaining alpha genes are dysfunctional, this is under study.

The case is reported of a 24-year-old Chinese patient with congenital hemolytic anemia (Hb 95 g/l, MCV 71 fl, MCHC 29 g%, reticulocytes 165% RBC). Clinical examination revealed jaundice and marked splenomegaly. Isoelectric focusing of Hb and Hb chains showed the absence of HbA, the presence of rapid Bart's and H Hb and the presence of an alpha chain variant alpha Q-Thailand, alpha 74 Asp----His (confirmation by fingerprinting of Hb). In vitro globin chain synthesis in reticulocytes and erythroblasts indicates that this variant is localized in an alpha-thal-2 chromosome. Furthermore, this variant does not exhibit any transcriptional defect of the alpha Q gene or any instability, since its association with a second alpha-thal-1 chromosome leads to a deficit of alpha chain production identical to that observed in Hb H disease (alpha alpha 0/alpha 0 alpha 0).