When the involved gene is ubiquitously expressed, the enzymopathy may be associated to extra-hematological signs such neuromuscular abnormalities, myopathy and mental retardation, as in the case of triosephosphate isomerase (32, 33), phosphoglycerate kinase deficiency (34) and phosphofructokinase deficiency (35). The gene discussed is TPI1; the disease is hyperinsulinemic hypoglycemia, familial, 4.