SLC6A8 and X-linked creatine transporter deficiency: In the present study, three of the 33 included patients (9%) had a genetic metabolic disease where targeted treatment is available; Glucose transporter protein type 1 deficiency syndrome (GLUT-1-DS) (SLC2A1-variant), Primary coenzyme Q10-deficinecy syndrome (COQ4-variant), and X-linked creatine transporter deficiency (CTD) (SLC6A8-variant).