Glucosephosphate isomerase (GPI) deficiency is an erythroenzymopathy characterized by chronic nonspherocytic hemolytic anemia. Prevalence is unknown but around 50 cases have been reported in the literature so far. GPI deficiency is the second most frequent glycolytic erythroenzymopathy after pyruvate kinase deficiency (see this term). Both males and females can be affected and the hemolytic anemia varies from mild to severe, with episodes of hemolytic crises triggered by viral or bacterial infections. Additional manifestations have been observed in a few patients and include a variable degree of intellectual deficit, hypotonia, muscle weakness, ataxia and dysarthria. Granulocyte disorders and splenomegaly have also been reported. In very rare cases, severe GPI deficiency may be associated with hydrops fetalis and neonatal death. GPI deficiency is inherited as an autosomal recessive trait and is caused by homozygous or compound heterozygous mutations in the GPI gene (19q13.1). To date, around 20 different GPI molecular variants have been identified in affected individuals. GPI is a ubiquitous enzyme that catalyses the conversion glucose-6-phosphate into fructose-6-phosphate, the second step in the glycolytic pathway. Diagnosis is made on the basis of the clinical picture in association with biochemical studies revealing erythrocyte GPI deficiency (between 7 and 60% of normal) and identification of a mutation in the GPI gene by molecular analysis. The differential diagnosis should include other rare causes of chronic hereditary nonspherocytic hemolytic anemia. Molecular prenatal diagnosis is feasible for families of an index case. Blood transfusions may be required for patients with severe anemia. Splenectomy has been shown to be beneficial, particularly during childhood. The prognosis is variable, depending on the severity of the anemia and on the presence of neurological manifestations.
Last update: August 2008