[Beta-thalassemia: clinical manifestations].

Monogenic diseases are very unevenly distributed throughout the world and beta-thalassemies are due chiefly to a large number of point mutations of the beta globine gene. The thalassemia trait (heterozygous thalassemia) can be asymptomatic and diagnosis is established by demonstration of an increased proportion of Hb A2. In the homozygous state (thalassemia major) hypochromic anemia is extremely severe because erythropoiesis is largely ineffective. Regular transfusion is necessary to prevent early death and transfusion therapy is usually initiated in the first year of life after biological diagnosis. Iron chelation is now capable of preventing transfusional haemachromatosis responsible for late mortality. 10% only of patients with homozygous beta-thalassemia have a syndrome of intermediate haematologic severity (thalassemia intermedia). Hb S--beta-thalassemia disease is characterised by a clinical course that resembles more that of Sickle Cell disease than to the thalassemia syndromes.