[1] Baylor Univ, Med Ctr, Inst Metab Dis, Dallas, TX USA
[2] Univ Texas, SW Med Ctr, Dept Neurol, Dallas, TX 75235 USA
[3] Univ Marburg, Childrens Hosp, Dept Neuropediat & Metab Dis, D-35032 Marburg, Germany
[4] Nemours Childrens Clin, Dept Pediat, Div Neurol, Jacksonville, FL USA
[5] Free Univ Amsterdam, Acad Hosp, Dept Clin Chem, NL-1081 HV Amsterdam, Netherlands
[6] Free Univ Amsterdam, Acad Hosp, Dept Pediat, NL-1081 HV Amsterdam, Netherlands