- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: PCS. Frequency: 1/1. (PMID:23084291)
- Skeletal muscle atrophy (HP:0003202): The presence of skeletal muscular atrophy (which is also known as amyotrophy). Evidence: PCS. Frequency: 1/2. (PMID:23084291)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Encephalopathy (HP:0001298): Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Poor head control (HP:0002421): Difficulty to maintain correct position of the head while standing or sitting. Infant head lag is observed when the head seems to flop around or lags posteriorly behind the trunk. Several articles have maintained that head lag should be absent by age 3 to 4 months. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Absent speech (HP:0001344): Complete lack of development of speech and language abilities. Evidence: PCS. (PMID:23084291)
- Abnormality of eye movement (HP:0000496): An abnormality in voluntary or involuntary eye movements or their control. Evidence: IEA. (OMIM:614932)
- Choreoathetosis (HP:0001266): Involuntary movements characterized by both athetosis (inability to sustain muscles in a fixed position) and chorea (widespread jerky arrhythmic movements). Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Dystonia (HP:0001332): An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Severe muscular hypotonia (HP:0006829): A severe degree of muscular hypotonia characterized by markedly reduced muscle tone. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Increased circulating lactate concentration (HP:0002151): Abnormally increased level of blood lactate (2-hydroxypropanoic acid). Lactate is produced from pyruvate by lactate dehydrogenase during normal metabolism. The terms lactate and lactic acid are often used interchangeably but lactate (the component measured in blood) is strictly a weak base whereas lactic acid is the corresponding acid. Lactic acidosis is often used clinically to describe elevated lactate but should be reserved for cases where there is a corresponding acidosis (pH below 7.35). Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Infantile onset (HP:0003593): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Increased CSF lactate (HP:0002490): Increased concentration of lactate in the cerebrospinal fluid. Evidence: PCS. Frequency: 2/2. (PMID:23084291)
- Dyskinesia (HP:0100660): A movement disorder which consists of effects including diminished voluntary movements and the presence of involuntary movements. Evidence: PCS. Frequency: 1/2. (PMID:23084291)
- Cataract (HP:0000518): A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule. Evidence: IEA. (OMIM:614932)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: IEA. (OMIM:614932)
- Sensorineural hearing impairment (HP:0000407): A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve. Evidence: IEA. (OMIM:614932)
- Autosomal recessive inheritance (HP:0000007): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele). Evidence: PCS. (PMID:23084291)
- Feeding difficulties in infancy (HP:0008872): Impaired feeding performance of an infant as manifested by difficulties such as weak and ineffective sucking, brief bursts of sucking, and falling asleep during sucking. There may be difficulties with chewing or maintaining attention. Evidence: PCS. Frequency: 1/2. (PMID:23084291)
- Decreased nerve conduction velocity (HP:0000762): A reduction in the speed at which electrical signals propagate along the axon of a neuron. Evidence: PCS. Frequency: 1/1. (PMID:23084291)
- Growth delay (HP:0001510): A deficiency or slowing down of growth pre- and postnatally. Evidence: TAS. (OMIM:614932)
- Leukodystrophy (HP:0002415): Leukodystrophy refers to deterioration of white matter of the brain resulting from degeneration of myelin sheaths in the CNS. Their basic defect is directly related to the synthesis and maintenance of myelin membranes. Symmetric white matter involvement at MRI is a typical finding in patients with leukodystrophies. Evidence: IEA. (OMIM:614932)
- Decreased mitochondrial complex III activity in liver tissue (HP:0006558): Decreased activity of complex III of the mitochondrion in the liver. Evidence: PCS. Frequency: 1/2. (PMID:23084291)
These phenotypes are associated with the disease combined oxidative phosphorylation defect type 13 (OMIM:614932).