- Elevated circulating C5 acylcarnitine concentration (HP:0035019): Concentration of C5 acylcarnitines in the blood circulation above the upper limit of normal. C5 acylcarnitines have a five-carbon acyl chain. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:79157)
- 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:79157)
- 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:79157)
- 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: Occasional (HP:0040283). (ORPHA:79157)
- Failure to thrive in infancy (HP:0001531). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:79157)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:79157)
- Autism (HP:0000717): Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication, and by restricted and repetitive behavior. Autism begins in childhood. It is marked by the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interest. Manifestations of the disorder vary greatly depending on the developmental level and chronological age of the individual (DSM-IV). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:79157)
- 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: Very rare (HP:0040284). (ORPHA:79157)
- 2-ethylhydracylic aciduria (HP:0033220): An increased concentration of 2-ethylhydracylic acid in the urine. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:79157)
These phenotypes are associated with the disease 2-methylbutyryl-CoA dehydrogenase deficiency (ORPHA:79157).