Enzyme Abnormalities in Red Cells

S ummary . Hereditary deficiencies involving eight enzymes of the Embden‐Meyer‐hof pathway, at least five involving the hexosemonophosphate shunt, and GSH metabolism, and at least two involving nucleotide metabolism, are known to be associated with haemolytic syndromes in man. Lactate dehydrogenase deficiency is also recognized, but is not associated with haemolysis. In addition, markedly aberrant enzyme activity ratios characterize a variety of dyserythropoietic disorders, both hereditary and acquired. In some disorders, haemolysis is the sole clinical manifestation; in others, dysfunction of the nervous system, the heart, the skeletal muscle, and the leucocytes may occur. The red cell may also mirror enzymopathies having expression in non‐haematopoietic tissues without a haemolytic syndrome being present. While double heterozygosity for two separate enzymopathies or for an enzymopathy and hereditary spherocytosis or elliptocytosis is recognized in a number of cases, clinical manifestations have thus far appeared minimal or non‐existent. In a recently described haemolytic syndrome uniquely large accumulations of cytidine and uridine nucleotides have been noted secondary to a severe deficiency of a pyrimidine specific 5’nucleotidase.