 KuvanTM is a form of tetrahydrobiopterin BH4, and is approved to help lower the blood levels of phenylalanine in people who have phenylketonuria PKU. LND patients have been found to have decreased BH4 in the spinal fluid and brain; BH4 is a precursor of dopamine, which has an effect on behavior. In an earlier study Dr Nyhan found that treatment of LND with 5-hydroxytryptophan and carbidopa abolished the self-injurious behavior but was uniformly transient. 