Polycythaemia rubra vera associated with unbalanced expression of the X chromosome and monoclonality of T lymphocytes

Polycythaemia rubra vera (PRV) was diagnosed in a 69-year-old Nigerian woman whose haemolysate revealed an electrophoretically slow-moving homogeneous band of the enzyme glucose 6-phosphate dehydrogenase (G6PD). Further biochemical characterization identified the enzyme as a new sporadic G6PD variant. Electrophoresis of the haemolysate of 4 children of the proposita identified in a daughter a large quantity of the slow-moving variant enzyme, and a much lower quantity of the normal type enzyme, thus, signifying an extremely unbalanced mosaic phenotype situation. All other family subjects studied, including 2 sons, had the normal enzyme type B, thus confirming the heterozygosity of the proposita at the G6PD locus. Homogenates of platelets, granulocytes and E-rosette-forming lymphocytes of the proposita showed an identical slow-moving band as the haemolysate, thus, suggesting the origin of these cells from a common progenitor cell which may be either the pluripotent stem cell (PSC) or another precursor cell at an earlier level of development than the PSC. While the observation of preferential production of the variant enzyme may be attributed to the presence on the X chromosome of a 'haemopoietic gene', its relevance to the etiology of PRV is unclear.