biostudies-literatureNasseri Moghaddam ZNIMH NIH HHSPatient-Centered Outcomes Research Institute408https://www.ebi.ac.uk/biostudies/studies/S-EPMC12333098biostudies-literatureUnknown20(1)<h4>Background</h4>Creatine transporter (CTD) and guanidinoacetate methyltransferase (GAMT) deficiencies are rare inborn errors of creatine metabolism, resulting in cerebral creatine deficiency. Patients with either condition commonly exhibit intellectual and developmental disabilities, often accompanied by behavior problems, delayed speech, seizures, and motor impairments. There is currently no efficacious treatment for CTD, while current management for GAMT requires lifelong treatment with a protein restricted diet and intake of high amounts of oral supplements. Efforts to conduct clinical trials on potential treatments for these disorders are made more difficult by the lack of clinical and patient-derived meaningful outcomes. A core outcome set (COS) can facilitate consistent use of outOrphanet journal of rare diseasesEstablishing a core outcome set for creatine transporter deficiency and guanidinoacetate methyltransferase deficiency.PMC12333098ZIC MH002961EACB-23059Miller JSLongo NSchulze AYoung SPBritz JWallis HPotter BKBaker SACafferty RThurm AWilliams KFBilder DATiller BHSalomons GSLipshutz GSSelucky TBogar RLi JStockler-Ipsiroglu SGraham CColler DPHall VReinhardt EKNasseri Moghaddam ZWheaton CPSmith MMercimek-Andrews SDeGrauw TJPasquali MBalog SfalseEstablishing a core outcome set for creatine transporter deficiency and guanidinoacetate methyltransferase deficiency.<h4>Background</h4>Creatine transporter (CTD) and guanidinoacetate methyltransferase (GAMT) deficiencies are rare inborn errors of creatine metabolism, resulting in cerebral creatine deficiency. Patients with either condition commonly exhibit intellectual and developmental disabilities, often accompanied by behavior problems, delayed speech, seizures, and motor impairments. There is currently no efficacious treatment for CTD, while current management for GAMT requires lifelong treatment with a protein restricted diet and intake of high amounts of oral supplements. Efforts to conduct clinical trials on potential treatments for these disorders are made more difficult by the lack of clinical and patient-derived meaningful outcomes. A core outcome set (COS) can facilitate consistent use of out2025-01-01T00:00:00Z2025 Aug2026-04-15T19:22:19.546Z2026-04-07T14:01:05.299ZS-EPMC123330984077564310.1186/s13023-025-03900-3