Ans 258. Chuvash polycythemia

Autosomal recessive disorder with features of both primary and secondary polycythemia, endemic to the mid-Volga River region of Russia (Chuvas); associated with homozygous mutation Arg200Trp in VHL gene (gene associated with von Hippel-Lindau syndrome); mutation impairs interaction of VHL with hypoxia-inducible factor 1 protein (HIF), allowing HIF to avoid destruction.