Diagnosis of Dihydropteridine Reductase Deficiency by Erythrocyte Enzyme Assay

Patients with hyperphenylalaninemia caused by dihydropteridine reductase (DHPR) deficiency, who show progressive cerebral degeneration despite adequate dietary treatment, may respond to neurotransmitter therapy if the diagnosis is made early.1 The diagnosis of this disorder is therefore urgent. A number of methods that had been shown to be of value in the diagnosis of the disease were discussed previously.2-4 A newer screening method for DHPR mutants that was based on measurement of the reduction state of biopterin in urine by high performance liquid chromatography was described by Milstien et al.5 Furthermore, recently leukocyte enzyme assays6,7 have been used in the diagnosis of DHPR deficiency.