Paroxysmal Nocturnal Hemoglobinuria: Evidence for Monoclonal Origin of Abnormal Red Cells

Paroxysmal nocturnal hemoglobinuria (PNH) was diagnosed in a 26-year-old Nigerian woman who subsequently died of amebic colitis. The patient’s red cells exhibited mosaicism with respect to glucose 6-phosphate dehydrogenase, in that some of them had the A, and some of them had the B variant of this enzyme (as expected in female subjects heterozygous at this sex-linked locus). The red cells bearing the PNH abnormality only had the B variant, suggesting that they all belonged to a single abnormal clone.