OBJECTIVES: To evaluate the usefulness of Phe loading test in patients for the diagnosis of guanosine triphosphate cyclohydrolase 1 deficiency (GTPCH). DESIGN AND METHODS: We studied one family composed of 13 members harbouring the Q89X mutation in the GTPCH gene, a non-related pediatric patient with GTPCH deficiency and 8 pediatric controls. 100 mg/kg of L-phenylalanine was orally administered, and blood spot samples were taken at baselines 1, 2, 4 and 6 h post-load. RESULTS: Two out of 7 pediatric patients showed a phenylalanine/tyrosine ratio higher than the previously reported cut-off value of 5.25 at 4 h, while 6 of the 7 adult patients showed a higher value. The only adult patient with a phenylalanine/tyrosine ratio below 5.25 at 4 h was asymptomatic. CONCLUSIONS: A cut-off value of 5.25 seems reliable for interpreting Phe loading test in adult patients with GTPCH deficiency, although a lower value should be established for pediatric patients.
OBJECTIVES: To evaluate the usefulness of Phe loading test in patients for the diagnosis of guanosine triphosphate cyclohydrolase 1 deficiency (GTPCH). DESIGN AND METHODS: We studied one family composed of 13 members harbouring the Q89X mutation in the GTPCH gene, a non-related pediatric patient with GTPCH deficiency and 8 pediatric controls. 100 mg/kg of L-phenylalanine was orally administered, and blood spot samples were taken at baselines 1, 2, 4 and 6 h post-load. RESULTS: Two out of 7 pediatric patients showed a phenylalanine/tyrosine ratio higher than the previously reported cut-off value of 5.25 at 4 h, while 6 of the 7 adult patients showed a higher value. The only adult patient with a phenylalanine/tyrosine ratio below 5.25 at 4 h was asymptomatic. CONCLUSIONS: A cut-off value of 5.25 seems reliable for interpreting Phe loading test in adult patients with GTPCH deficiency, although a lower value should be established for pediatric patients.
Authors: Eduardo López-Laso; Araceli Sánchez-Raya; Juan Antonio Moriana; Eduardo Martínez-Gual; Rafael Camino-León; María Elena Mateos-González; Juan Luis Pérez-Navero; Juan José Ochoa-Sepúlveda; Aida Ormazabal; Thomas Opladen; Christine Klein; José Ignacio Lao-Villadóniga; Katrin Beyer; Rafael Artuch Journal: J Neurol Date: 2011-05-10 Impact factor: 4.849
Authors: K Kusmierska; E E W Jansen; C Jakobs; K Szymanska; E Malunowicz; D Meilei; B Thony; N Blau; J Tryfon; D Rokicki; E Pronicka; J Sykut-Cegielska Journal: J Inherit Metab Dis Date: 2009-01-07 Impact factor: 4.982