Heterogeneity and gene-geography of β-thalassemia in Georgia.

Georgia is situated between 44° and 41° of Northern Width. This is an area which belongs to "Malarial zone" of the Earth. This country is characterized by peculiar geographic contrasts as well as by peculiar ethnic variety of population on the small territory. So it represents an important region for study of thalassemias. The main purpose of this work is to present nonpublished results of long-term clinical and population investigations for study of heterogeneity and gene-geography of β-thalassemia in Georgia. About 11.428 practically healthy persons were investigated in different Georgian and non-Georgian ethno-territorial groups under expeditionary conditions and about 600 patients (probands and members of their families)--in clinical laboratory. Screening tests under expeditionary conditions and special tests for the differentiation of thalassemias in clinical laboratory as well as familial-genetic investigaton were performed for diagnostics of thalassemias. Common form of β-thalassemia in Georgia was found β(A2)--thalassemia wich was revealed not only in Georgian families but also among Azerbaijanians, Armenians,Daghestanians, Greeks, Georgian Jews, leaving in this country. Very rare δβ(F)--thalassemia was also revealed. From genetic point of view most heterogenous was found thalassemia intermedia, due to different combinations of α, β,δβ--thalassemias. Population study revealed regularities of gene-geography of β-thalassemia in Georgia: a) statistical significantly higher gene frequency in lowlands and valleys than in highlands, b) Difference of gene frequency in Georgian and non-Georgian ethnic groups in similar geographic conditions, c) Direct correlation between β-thalassemia gene frequency and degree of malariogeneity of territory, d) Direct correlation between β-thalassemia gene frequency and intensity of former malaria focuses, e) Direct correlation between gene frequency and p. vivax distribution area (in the past). Gene-geographic card of "Distribution of β-thalassemia gene in ethno-territorial groups and malariogenic zones of Georgia" was made up. By means of this cord β-thalassemia gene frequency at non-investigated territories of Georgia was prognosed. Prognosis justified. Also this card may be recommended for use in other countries taking into consideration malaria distribution (even in the past) as well as ethnic structure of population.