Hereditary haemoglobin disorders in Brazil.

The data on the incidence and variability of hereditary haemoglobin (Hb) disorders in Brazil are reviewed. The most common abnormalities are HbS, HbC and beta-thalassaemias. Both homozygotes and compound heterozygotes for these genes (i.e., HbS/HbC disease, S/beta-thalassaemia, C/beta-thalassaemia) are common, owing to the free miscegenation of populations of Mediterranean and African ancestry. The diversity of beta-thalassaemias is similar to that observed in other regions. beta(0)-Thalassaemia is more frequent than the beta(+) variant among affected individuals. Most patients are descendants of Italian immigrants but occasional cases have other racial origins. Patients with thalassaemia major are mostly beta (0) homozygotes, while thalassaemia intermedia is more heterogeneous, including a variety of genotypes. alpha-Thalassaemias are not common although cases of HbH disease have been reported. Isolated examples of several Hb variants have been described, and two abnormal Hb were first found in Brazil: Hb Porto Alegre and Hb Niteroi.