This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor.

Many patients have significant developmental delays despite therapy, develop brain abnormalities, and are prone to sudden death.

The reason is not completely clear, but might be related to the accumulation of dihydrobiopterin and abnormal metabolism of folic acid.

[1] Response to treatment is variable and the long-term and functional outcome is unknown.

To provide a basis for improving the understanding of the epidemiology, genotype/phenotype correlation and outcome of these diseases their impact on the quality of life of patients, and for evaluating diagnostic and therapeutic strategies a patient registry was established by the noncommercial International Working Group on Neurotransmitter Related Disorders (iNTD).