Phenotype-genotype correlation in Sicilian patients with Hb H

We studied 15 Sicilian subjects with Hb H disease correlating clinical examinations with hematological and molecular data. Seven different α-thal mutations were identified: four deletion types (--MED, --CAL, -α3.7, -α4.2) and three nondeletion types (αNcolα, αHphα, αCSα). All the patients had a zero-gene chromosome (--MED or --CAL), while the third α gene was deleted (-α3.7, -α4.2) or inactive (αNcolα, αHphα, αCSα). In patients with the nondeletion genotype the analysis of hematological values revealed lower levels of RBC and Hb A2 and significantly higher levels of Hb H. The clinical variability was remarkable, ranging from totally asymptomatic conditions, casually diagnosed, to severe thalassemia intermedia with marked hemolytic crises, liver and spleen enlargement and the necessity for frequent transfusions. The genotype did not justify the gravity of the phenotype in every case, and the differences in clinical manifestations, also notable, are not easily explainable in subjects who apparently have the same genotype.