The measurement blood and brain phenylalanine level in hyperphenylalaninemic patients and evaluation the efficiency of the treatment

Defects in either PAH or the production of recycling of BH4 may result in HPA and if left untraeted, HPA can lead to profound brain damage. Today worlwide advocate lifelong adherence to a PHE-restricted diet to maintain blood PHE concentrations within recommended treatment ranges and nowadays the alternative treatment methods are very popular. One of them is the BH4 treatment which is cofactor of PAH enzyme and is thought to be increased the activity and function of the enzyme. For determining response to BH4 should be performed BH4 loading test in HPA patients.In this study, we determined the BH4 responsive patients by using the BH4 loading test. We determined significant decline in plasma PHE concentration after oral BH4 administration in 16 of 41 patients but the PHE tolerance of one of this patients couldn?t be increased adequatly and this patient has been accepted as non-responsive in the treatment period. Two patients had the disorders of BH4 metabolism. The other patients were in mild or moderate HPA classes generally similar to the literature knowledge.The pathogenesis of brain dysfunction in HPA is still unknown, but it?s believed that the most important reason is the brain PHE level. Therefore we investigated in our ten HPA patients the PHE level in the brain by using the MRS technique. According to the results the brain PHE levels were decreased after the treatment. This reduction was statistically significant in the patients who are being treated with PHE-restricted diet, but this was not significant in the patients who are followed under BH4 therapy. We thought that the numbers of patients and the individual differences of the blood-brain barrier can be affected tis result.As a result, the assessment of under different dietetic conditions or following oral BH4 therapy can provide a new biochemical parameter to be included among critaria for assessing patients with regard to discontinuation or continuation of therapy. Therefore, MRS investigations may have a potential for optimising individual treatment strategies. But we need ofcourse more extensive studies to standardize this method.