RESUMO
The aim of this study was to define the spectrum of alpha-thalassemia determinants existing in Jordan. A total 286 suspected alpha-thalassemia subjects including 29 hemoglobin Hb [Hb H] patients were examined by polymerase chain reaction and restriction enzyme digestion. Polymerase chain reaction product was examined by agarose gel electrophoresis. Five different alpha-thalassemia determinants were characterized in 336 chromosomes. The most prevalent alpha -thalassemia determinant was the single gene deletion -alpha[3.7] [45%]. The non-gene deletion alpha [5nt] accounted for 27% of thalassemic chromosomes, followed by the non-gene deletional determinant alpha [T-Saudi][23%]. The two-gene deletional determinant -[MED] was characterized only in 4% of thalassemic chromosomes. Triplicated alpha -gene determinant was observed in two heterozygous individuals [alpha alpha alpha / alpha alpha]. Four different genotypes were found to be responsible for Hb H disease. Homozygosity for the non-deletional determinant alpha[T-Saudi] [alpha T-Saudi] alpha/alpha T-Saudi]alpha] was observed in the majority of those patients [76%] and was found to be associated with high Hb H levels. Less commonly, Hb H disease occurred as a result of compound hterozygosity between -[MED] determinant with other determinants; [-[MED] /alpha [T-Saudi] alpha] [--MED]/ alpha[5nt] alpha], [--[MED]/ -alpha[37] alpha]. The outcome of this pilot study provides valuable and basic information, about the spectrum of a-thalassemia mutations in Jordan that might be useful in setting a strategy for molecular diagnosis of alpha-thalassemia carrier status and Hb H disease in this country