Generally, the majority of individuals with<unk>  express the following symptoms with varying levels of severity: developmental delay and regression, mental retardation, and abnormalities in expressive and cognitive speech. However, several studies have shown a wider variety of symptoms including, but not limited to attention deficit and hyperactivity with impulsivity, myopathy, hypotonia, semantic-pragmatic language disorder, oral dyspraxia, extrapyramidal movement disorder, constipation, absent speech development, seizures, and epilepsy. Furthermore, symptoms can significantly vary between hemizygous males and heterozygous females, although, symptoms are generally more severe in hemizygous males. Hemizygous males more commonly express seizures, growth deficiency, severe mental retardation, and severe expressive language impairment. Heterozygous females more commonly express mild intellectual disability, impairments to confrontational naming and verbal memory, and learning and behavior problems.
Creatine transporter defect
N-Acetylglutamate synthase deficiency
Cerebral creatine deficiency
Mitochondrial complex II deficiency
Lysosomal storage disease
D-bifunctional protein deficiency
Mitochondrial trifunctional protein deficiency
Trinucleotide repeat disorder