Congenital polycythemia in Chuvashia

Area of Science:

• Genetics
• Hematology
• Population Studies

Background:

• Familial and congenital polycythemia is prevalent in the Chuvash population, inherited in an autosomal recessive pattern.
• This condition is distinct from polycythemia caused by high oxygen affinity hemoglobin or reduced erythrocyte 2,3-diphosphoglycerate.
• Hundreds of individuals in the Chuvash population are affected by this endemic form of polycythemia.

Purpose of the Study:

• To investigate the genetic basis of familial and congenital polycythemia in the Chuvash population.
• To determine the linkage of Chuvash polycythemia with the erythropoietin (EPO) gene and EPO receptor gene.
• To explore the etiology of this unique endemic polycythemia.

Main Methods:

• Studied six polycythemic Chuvash patients (<20 years) and 12 first-degree relatives from unrelated families.
• Measured hemoglobin levels, platelet, and white blood cell counts.
• Assessed serum erythropoietin concentrations using radioimmune and functional assays.
• Performed Southern blot analysis for Bgl 2 erythropoietin gene polymorphism.
• Utilized polymerase chain reaction (PCR) for GGAA and GA minisatellite polymorphism analysis of the erythropoietin receptor gene.

Main Results:

• Polycythemic patients exhibited markedly elevated hemoglobin levels (mean 22.6 +/- 1.4 g/dL) with normal blood cell counts.
• Serum erythropoietin concentrations were significantly higher in polycythemic patients compared to unaffected family members.
• Analysis suggested no linkage between Chuvash polycythemia and the erythropoietin gene or erythropoietin receptor gene.

Conclusions:

• Chuvash polycythemia is likely a secondary form of familial and congenital polycythemia.
• The etiology of this endemic condition remains unknown.
• This represents the only described endemic form of familial and congenital polycythemia.