Defining tetrahydrobiopterin responsiveness in phenylketonuria: Survey results from 38 countries

R A F Evers, A M J van Wegberg, K Ahring, S Beblo, A Bélanger-Quintana, A M Bosch, A Burlina, J Campistol, T Coskun, F Feillet, M Giżewska, S C J Huijbregts, S Kearney, M Langeveld, V Leuzzi, F Maillot, A C Muntau, J C Rocha, C Romani, F K TrefzA MacDonald, F J van Spronsen