The clinical phenotype of beta and delta beta thalassemias in Greece.

Based on precise evaluation of hematological findings and clinical manifestations, the relationship between genotype and clinical phenotype was studied in 475 Greek patients with beta and delta beta thalassemias. Almost all known genotypes are included in this series, but the most frequent was homozygous beta th high A2 (71.6%), beta th/beta th silent (7.4%), beta th/delta beta oth high F (6.3%) and beta th/beta th Dutch (6.3%). In general, the phenotype was related to the genotype, though clinical heterogeneity was detected among patients with the same genotype. The severe type of thalassemia major was most commonly found in homozygous beta th patients mainly of beta o/beta o and beta o/beta + genotypes while homozygous beta + patients had milder clinical manifestation. Furthermore a small group of patients, characterized as homozygous beta ++ (HbF less than 30%) had mild thalassemia intermedia. In addition mild thalassemia intermedia was principally related with homozygous delta beta oth, and compound heterozygous beta th/beta th silent I, and less frequently with other genotypes such as compound heterozygous with beta th/beta th Dutch, beta th/beta th silent II, beta th/delta beta oth high F or Lepore. It was shown that precise genetic characterization and clinical evaluation is of primary importance in predicting the prognosis and formulating the proper treatment for the individual patient with thalassemia.