Measurement of neurotransmitter metabolites in the cerebrospinal fluid of phenylketonuric patients under dietary treatment

The plasma Phe levels were averaged over periods of 12 months and were in the range according to the recommendations for treatment recently reported from German Working Group for Metabolic Diseases (Burgard et al 1999). Interestingly, tyrosine was below the normal range in four patients, and in the range in the remaining patients. All the examined patients showed low concentrations neurotransmitter metabolites in CSF. Our data showed a severe deÐ- of dopamine and serotonin metabolites in the central nervous system of adolescents still on diet. To our knowledge, this is the Ðrst report inwhich a deÐciency of dopamine and serotonin metabolism has been detected in -treated PKU patients still on diet. Indeed, it was reported that only patients treated or o† diet showed low levels of CSF HVA and 5-HIAA (Scriver et al 1995). investigate whether the decrease in dopamine and serotonin metabolites in could be related to neural cell damage or dysfunction, we determined NAA NAAG concentrations in the CSF of the patients. Both NAA and NAAG are almost exclusively in neurons (Powels and Frahm 1997). NAA concentrations normal in all samples (\\7.4 kmol/L, normal \\7.4, n\\25) except one in which was just above normal (patient 4, NAA\\9.0 kmol/L); NAAG concentrations normal in all samples examined (up to 8.7 kmol/L, normal 0.7È12.7, n\\25). results, even if restricted to a limited number of patients, raise the following . (a) PKU needs a careful neurological follow-up during adolescence and . (b) The question whether long-term dietary treatment can or should be or discontinued is still unresolved. (c) Diet modiÐcations including di†erent acid supplementation (i.e. increased amount of tyrosine) should be considered an additional treatment in the long-term diet.