- Global developmental delay (HP:0001263): A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:35704)
- Cognitive impairment (HP:0100543): Abnormal cognition is characterized by deficits in thinking, reasoning, or remembering. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:35704)
- Reduced tissue arginine:glycine amidinotransferase activity (HP:6000572): Activity of L-arginine:glycine amidinotransferase (GATM; EC 2.1.4.1) in the tissues below the lower limit of normal. GATM activity can be measured in multiple tissues including leukocytes and cultured fibroblasts. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:35704)
- Delayed speech and language development (HP:0000750): A degree of language development that is significantly below the norm for a child of a specified age. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Decreased serum creatinine (HP:0012101): An abnormally reduced amount of creatinine in the blood. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Reduced brain creatine level by MRS (HP:0025051): A decrease in the level of creatine in the brain identified by magnetic resonance spectroscopy (MRS). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Reduced circulating creatine concentration (HP:0034292): An reduction below the normal range of creatine in the blood circulation. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Decreased CSF creatinine concentration (HP:0034597): Concentration of creatinine in the cerebrrospinal fluid below the lower limit of normal. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Decreased urine guanidinoacetic acid level (HP:0034888): The concentration of guanidinoacetic acid in the urine, normalized for urine concentration, is below the lower limit of normal. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Decreased urine creatinine level (HP:6000115): The amount of creatinine in the urine, normalized for urine concentration, is below the lower limit of normal. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Decreased urinary creatine level (HP:6000748): The amount of creatine in the urine, normalized for urine concentration, is below the lower limit of normal. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:35704)
- Atypical behavior (HP:0000708): 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. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:35704)
- Seizure (HP:0001250): 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. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:35704)
- Hypotonia (HP:0001252): Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:35704)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:35704)
These phenotypes are associated with the disease L-Arginine:glycine amidinotransferase deficiency (ORPHA:35704).