MedGen

The creatine deficiency disorders (CDDs), inborn errors of creatine metabolism and transport, comprise three disorders: the creatine biosynthesis disorders guanidinoacetate methyltransferase (GAMT) deficiency and L-arginine:glycine amidinotransferase (AGAT) deficiency; and creatine transporter (CRTR) deficiency. Developmental delay and cognitive dysfunction or intellectual disability and speech-language disorder are common to all three CDDs. Onset of clinical manifestations of GAMT deficiency (reported in ~130 individuals) is between ages three months and two years; in addition to developmental delays, the majority of individuals have epilepsy and develop a behavior disorder (e.g., hyperactivity, autism, or self-injurious behavior), and about 30% have movement disorder. AGAT deficiency has been reported in 16 individuals; none have had epilepsy or movement disorders. Clinical findings of CRTR deficiency in affected males (reported in ~130 individuals) in addition to developmental delays include epilepsy (variable seizure types and may be intractable) and behavior disorders (e.g., attention deficit and/or hyperactivity, autistic features, impulsivity, social anxiety), hypotonia, and (less commonly) a movement disorder. Poor weight gain with constipation and prolonged QTc on EKG have been reported. While mild-to-moderate intellectual disability is commonly observed up to age four years, the majority of adult males with CRTR deficiency have been reported to have severe intellectual disability. Females heterozygous for CRTR deficiency are typically either asymptomatic or have mild intellectual disability, although a more severe phenotype resembling the male phenotype has been reported. [from GeneReviews]

Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70. [from HPO]

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain. [from HPO]

Melkersson-Rosenthal syndrome is characterized by chronic swelling of the face, peripheral facial palsy, which may be bilateral and may tend to relapse, and in some cases ligua plicata (fissured tongue). The swelling is localized especially to the lips. Onset is usually in childhood or adolescence (summary by Kunstadter, 1965). [from OMIM]

Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will. [from HPO]

An abnormality in the sound (volume) or cadence (rate) of speech. [from HPO]

A mode of inheritance that is observed for traits related to a gene encoded on the X chromosome. [from HPO]

A generalized-onset seizure is a type of seizure originating at some point within, and rapidly engaging, bilaterally distributed networks. The networks may include cortical and subcortical structures but not necessarily the entire cortex. [from HPO]

X-linked form of disease. [from MONDO]

An X-linked intellectual deficiency in which not enough information is known, reported or published to indicate whether a gene causes non-syndromic or syndromic presentations. [from MONDO]

A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures. [from HPO]

Seizures characterized by olfactory phenomena as its first clinical manifestation. [from HPO]

A seizure characterized by sensory phenomena including tingling, numbness, electric-shock like sensation, pain, sense of movement, or desire to move as its first clinical manifestation. [from HPO]

Clinical or subclinical disturbances of cortical function due to a sudden, abnormal, excessive, and disorganized discharge of brain cells. Clinical manifestations include abnormal motor, sensory and psychic phenomena. Recurrent seizures are usually referred to as epilepsy or 'seizure disorder.' [from MONDO]

A group of neurologic disorders caused by alterations to the biochemical functioning of the brain. They are characterized by an altered level of consciousness and depressed cerebral functioning. [from NCI]

Neurodevelopmental disorder is a behavioral and cognitive disorder with onset during the developmental period that involves impaired or aberrant development of intellectual, motor, or social functions. [from SNOMEDCT_US]