PHENOTYPES OF INDIVIDUALS WITH A BETA-THAL CLASSICAL ALLELE ASSOCIATED EITHER WITH A BETA-THAL SILENT ALLELE OR WITH ALPHA-GLOBIN GENE TRIPLICATION

Background and Objective. beta thalassemia intermedia has its origins in compound heterozygosity for many different beta that defects or in an interaction of a beta thal defect with altered alpha cluster. Two s pecific genetic associations (beta thal/beta(+)-101 C-->T and beta tha l + alpha alpha alpha or alpha alpha alpha alpha) have been described in recent years as being determining a phenotype similar to that of si mple beta thal heterozygote or, alternatively, a clinical picture of t halassemia intermedia. Methods. A detailed study on this subject was c arried out on 55 patients divided into 2 groups. Group I consisted of 20 patients, 17 of whom (Group Ia) had a beta thal/beta(+)-101 C-->T g enotype and 3 (Group Ib) had a beta thal/beta IVS II-844 C-->G genotyp e. Group II consisted of 35 patients with beta thal association +alpha alpha alpha or alpha alpha alpha alpha(anti3.7). The methods of study have already been described in a previous issue.(10) Results. Thirty percent of group Ia and 25% of group II were virtually asymptomatic, w hile the others presented the thalassemia intermedia phenotype. This s econd phenotype is generally milder in patients of group I and even le ss so in those of group II. In the former there is a higher level of H bF; in the second there is more marked alpha/beta+gamma globin synthes is imbalance. The severity of the phenotype has no connection with tha t of the beta that defect. The patients of group Ib all presented thal assemia intermedia. Interpretation and Conclusions. The definite clini cal pictures of groups I and II are quite common in the Italian popula tion and should therefore be well understood, especially for proper ap plication of preventive measures against thalassemia major. (C) 1997, Ferrata Storti Foundation.