Diagnosis and management of rare congenital nonimmune hemolytic disease.

Rare, congenital nonimmune hemolytic disorders of the erythrocyte, although uncommon, are important causes of anemia in the child and adult. These are a heterogeneous group of diseases that disrupt normal erythrocyte structure and function in varying ways. Predominant are abnormalities of hemoglobin stability, defects of erythrocyte metabolism, and disorders of erythrocyte hydration. Unstable hemoglobinopathies may lead to chronic or episodic hemolysis. Perturbation of critical enzymes of the Embden-Meyerhof pathway lead to altered erythrocyte metabolism and chronic hemolysis. Disorders of erythrocyte hydration are an under-recognized cause of hemolytic anemia. Beyond pathophysiologic mechanisms of disease, clinical, laboratory, and genetic heterogeneity characterize this group of disorders. Often, they are underdiagnosed or misdiagnosed. This review discusses pathophysiology, inheritance, clinical findings, laboratory manifestations, and management considerations in several rare nonimmune hemolytic diseases including the unstable hemoglobins, disorders of erythrocyte metabolism, and abnormalities of erythrocyte hydration.