tailieunhanh - Chapter 101. Hemolytic Anemias and Anemia Due to Acute Blood Loss (Part 10)

Epidemiology G6PD deficiency is widely distributed in tropical and subtropical parts of the world (Africa, Southern Europe, the Middle East, Southeast Asia, and Oceania) (Fig. 101-5) and wherever people from those areas have migrated; a conservative estimate is that at least 400 million people have a G6PD-deficiency gene. In several of these areas, the frequency of a G6PD-deficiency gene may be as high as 20% or more. It would be quite extraordinary for a trait that causes significant pathology to spread widely and reach high frequencies in many populations without conferring some biologic advantage. Indeed, G6PD is one of. | Chapter 101. Hemolytic Anemias and Anemia Due to Acute Blood Loss Part 10 Epidemiology G6PD deficiency is widely distributed in tropical and subtropical parts of the world Africa Southern Europe the Middle East Southeast Asia and Oceania Fig. 101-5 and wherever people from those areas have migrated a conservative estimate is that at least 400 million people have a G6PD-deficiency gene. In several of these areas the frequency of a G6PD-deficiency gene may be as high as 20 or more. It would be quite extraordinary for a trait that causes significant pathology to spread widely and reach high frequencies in many populations without conferring some biologic advantage. Indeed G6PD is one of the best characterized examples of genetic polymorphisms in the human species. Clinical field studies and in vitro experiments strongly support the view that G6PD deficiency has been selected by Plasmodium falciparum malaria by virtue of the fact that it confers a relative resistance against this highly lethal infection. Whether this protective effect is exerted mainly in hemizygous males or in females heterozygous for G6PD deficiency is still not clear. Different G6PD variants underlie G6PD deficiency in different parts of the world. Some of the more widespread variants are G6PD Mediterranean on the shores of the Mediterranean Sea in the Middle East and in India G6PD A- in Africa and in Southern Europe G6PD Vianchan and G6PD Mahidol in Southeast Asia G6PD Canton in China and G6PD Union worldwide. The heterogeneity of polymorphic G6PD variants is proof of their independent origin and it supports the notion that they have been selected by a common environmental agent in keeping with the concept of convergent evolution. Figure 101-5 Epidemiology of G6PD deficiency throughout the world. The different shadings indicate increasingly high levels of prevalence up to about 20 the different colored symbols indicate individual genetic variants of G6PD each one having a different mutation. From L