English: Fig. 2. Symptom inventory outcomes in patients with tetrahydrobiopterin deficiency before and after treatment with sapropterin. Seven patients with low tetrahydrobiopterin levels in their CSF who were treated with sapropterin 20 mg/kg showed significant reductions in their follow-up SIQ and BDI scores. Average BDI scores decreased from 42.86 (s.d. 11.08) to 27.71 (s.d. 19.05), although, t tests revealed that the change was not statistically significant, t = 1.85, p < 0.09. Average Suicidal Ideation Questionnaire score decreased from 60.14 (s.d. 14.71) to 38.29 (s.d. 21.72), t tests revealed that the change was statistically significant, t = 2.25, p < 0.04.