(a) This patient received tandem mass spectrometry, urinary neopterin and biopterin analysis, and determination of dihydropteridine reductase (DHPR) activity in dried blood spots.
Dried blood spots are the best sample for the simultaneous measurement of amino acids (phenylalanine and tyrosine), pterins (neopterin and biopterin), and dihydropteridine reductase activity from a single specimen.
Diagnosis relies on the measurement of pterin metabolites in urine, dihydropteridine reductase in blood spots, neurotransmitters and pterins in the CSF and on the demonstration of reduced enzyme activity (red blood cells or fibroblasts) or causative mutations in the relative genes.