X-linked creatine deficiency

X-linked creatine deficiency is a rare condition that primarily affects the brain. Signs and symptoms generally develop before age 2 and may include mild to severe intellectual disability; delayed speech development, behavioral problems (i.e. autistic features, hyperactivity), and seizures. Less commonly, affected people may have distinctive facial features, heart abnormalities, and gastrointestinal disorders. X-linked creatine deficiency is caused by changes (mutations) in the SLC6A8 gene and is inherited in an X-linked manner. Treatment with high doses of creatine monohydrate, L-arginine, and L-glycine has been used to treat some of the symptoms associated with X-linked creatine deficiency with variable success

Reference : Rarediseases