- Hypertonia (HP:0001276): A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move. Evidence: PCS. Frequency: 2/2. (PMID:15537906)
- Cholestasis (HP:0001396): Impairment of bile flow due to obstruction in bile ducts. Evidence: PCS. Frequency: 2/2. (PMID:15537906)
- Congenital onset (HP:0003577): A phenotypic abnormality that is present at birth. Evidence: PCS. (PMID:15537906)
- 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. (OMIM:609060)
- Global brain atrophy (HP:0002283): Unlocalized atrophy of the brain with decreased total brain matter volume and increased ventricular size. Evidence: PCS. Frequency: 1/2. (PMID:15537906)
- Hepatomegaly (HP:0002240): Abnormally increased size of the liver. Evidence: TAS. (OMIM:609060)
- Delayed myelination (HP:0012448): Delayed myelination. Evidence: TAS. (OMIM:609060)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: IEA. (OMIM:609060)
- Elevated lactate:pyruvate ratio (HP:0032653): An abnormal increase in the molar ratio of lactate to pyruvate in the blood circulation. Evidence: IEA. Frequency: 2/2. (PMID:15537906)
- Nystagmus (HP:0000639): Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms. Evidence: TAS. (OMIM:609060)
- Reduced eye contact (HP:0000817): A reduced frequency or duration of eye contact. Evidence: TAS. (OMIM:609060)
- Metabolic acidosis (HP:0001942): Metabolic acidosis (MA) is characterized by a fall in blood pH due to a reduction of serum bicarbonate concentration. This can occur as a result of either the accumulation of acids (high anion gap MA) or the loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic MA). By definition, MA is not due to a respirary cause. Evidence: PCS. Frequency: 2/2. (PMID:15537906)
- Basal ganglia cysts (HP:0006799). Evidence: PCS. Frequency: 1/2. (PMID:15537906)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: TAS. (OMIM:609060)
- Axial hypotonia (HP:0008936): Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk. Evidence: TAS. (OMIM:609060)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: PCS. Frequency: 1/2. (PMID:15537906)
- Hypokinesia (HP:0002375): Abnormally diminished motor activity. In contrast to paralysis, hypokinesia is not characterized by a lack of motor strength, but rather by a poverty of movement. The typical habitual movements (e.g., folding the arms, crossing the legs) are reduced in frequency. Evidence: PCS. Frequency: 1/2. (PMID:15537906)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: PCS. Frequency: 2/2. (PMID:15537906)
- Feeding difficulties (HP:0011968): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: TAS. (OMIM:609060)
- Decreased activity of mitochondrial complex III (HP:0011924): A reduction in the activity of the mitochondrial respiratory chain complex III, which is part of the electron transport chain in mitochondria. Evidence: PCS. Frequency: 1/1. (PMID:15537906)
- Decreased activity of mitochondrial ATP synthase complex (HP:0011925): A reduction in the activity of the mitochondrial proton-transporting ATP synthase complex, which makes ATP via oxidative phosphorylation, and is sometimes described as Complex V of the electron transport chain. Evidence: PCS. Frequency: 1/1. (PMID:15537906)
- 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. (PMID:15537906)
- Increased CSF lactate (HP:0002490): Increased concentration of lactate in the cerebrospinal fluid. Evidence: TAS. (OMIM:609060)
- Decreased activity of mitochondrial complex I (HP:0011923): A reduction in the activity of the mitochondrial respiratory chain complex I, which is part of the electron transport chain in mitochondria. Evidence: PCS. Frequency: 1/1. (PMID:15537906)
- 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:15537906)
- Decreased activity of mitochondrial complex IV (HP:0008347): A reduction in the activity of the mitochondrial respiratory chain complex IV, which is part of the electron transport chain in mitochondria. Evidence: PCS. Frequency: 1/1. (PMID:15537906)
- Intrauterine growth retardation (HP:0001511): An abnormal restriction of fetal growth with fetal weight below the tenth percentile for gestational age. Evidence: PCS. Frequency: 1/2. Onset: Fetal onset (HP:0011461). (PMID:15537906)
- Spasticity (HP:0001257): A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes. Evidence: TAS. (OMIM:609060)
- Fulminant hepatic failure (HP:0004448): Hepatic failure refers to the inability of the liver to perform its normal synthetic and metabolic functions, which can result in coagulopathy and alteration in the mental status of a previously healthy individual. Hepatic failure is defined as fulminant if there is onset of encephalopathy within 4 weeks of the onset of symptoms in a patient with a previously healthy liver. Evidence: PCS. Frequency: 2/2. Onset: Neonatal onset (HP:0003623). (PMID:15537906)
These phenotypes are associated with the disease hepatoencephalopathy due to combined oxidative phosphorylation defect type 1 (OMIM:609060).