Possible causes for a normocytic hyperregeneratory anemia are beside an 
incomplete treatment of iron deficiency, vitamin B12 deficiency or folic acid 
deficiency notably a hemolysis. After exclusion of other causes of hemolysis 
like immune hemolytic anemias, microangiopathic hemolytic anemias and 
hemoglobinopathies, an enzyme deficiency of erythrocytes should be considered. 
By far the most common form worldwide is the Glucose-6-phosphate deficiency. In 
the most frequent variants of this disease hemolysis occurs only during stress, 
imposed for example by infection, "oxidative" drugs or after ingestion of fava 
beans. The most serious clinical complication of the Glucose-6-phosphate 
deficiency is the rarely observed neonatal icterus. Some enzyme variants can 
cause chronic hemolysis which is described as chronic nonsperocytic hemolytic 
anemia. This form of chronic anemia can also be caused by other enzyme 
deficiencies, most frequently by the Pyruvate kinase deficiency. All other 
deficiencies of glycolytic enzymes are even rarer. It should be noted that in 
some of these very rare forms neurological rather than hematological symptoms 
predominate the clinical syndrome. If there is suspicion, on the basis of 
clinical symptoms and/or familial history, diagnosis of an enzyme deficiency can 
be achieved relatively easy by measurement of the enzyme activity. Accurate 
diagnosis might be helpful in therapeutic decisions (e.g. splenectomy in certain 
forms) and it is essential for genetic counseling, since certain deficiencies 
are transmitted as autosomal recessive disorders (e.g. pyruvate kinase 
deficiency), while the most common form, the glucose-6-phosphate dehydrogenase 
deficiency is linked to the X-chromosome.