- Lethargy (HP:0001254): A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks. Evidence: PCS. Frequency: 2/2. (PMID:29478781)
- 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. (PMID:29478781)
- Bilateral tonic-clonic seizure (HP:0002069): A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Elevated circulating creatine kinase activity (HP:0003236): The activity of creatine kinase in the blood circulation is above the upper limit of normal. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Ketoacidosis (HP:0001993): Acidosis resulting from accumulation of ketone bodies. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- 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: PCS. Frequency: 1/2. (PMID:29478781)
- Short stature (HP:0004322): A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms). Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Rhabdomyolysis (HP:0003201): Breakdown of muscle fibers that leads to the release of muscle fiber contents (myoglobin) into the bloodstream. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- 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: 2/2. (PMID:29478781)
- 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: PCS. (PMID:29478781)
- Gait imbalance (HP:0002141). Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Elevated serum anion gap (HP:0031962): An abnormally high value of the serum anion gap (the sum of serum chloride and bicarbonate concentrations subtracted from the serum sodium concentration). Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Hypoglycemia (HP:0001943): A decreased concentration of glucose in the blood. Evidence: PCS. Frequency: 2/2. (PMID:29478781)
- Hyperammonemia (HP:0001987): An increased concentration of ammonia in the blood. Evidence: PCS. Frequency: 2/2. (PMID:29478781)
- 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:29478781)
- Ankle flexion contracture (HP:0006466). Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Lactic acidosis (HP:0003128): An abnormal buildup of lactic acid in the body, leading to acidification of the blood and other bodily fluids. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- Exercise intolerance (HP:0003546): A functional motor deficit where individuals whose responses to the challenges of exercise fail to achieve levels considered normal for their age and gender. Evidence: PCS. Frequency: 2/2. (PMID:29478781)
- Dilated cardiomyopathy (HP:0001644): Dilated cardiomyopathy (DCM) is defined by the presence of left ventricular dilatation and left ventricular systolic dysfunction in the absence of abnormal loading conditions (hypertension, valve disease) or coronary artery disease sufficient to cause global systolic impairment. Right ventricular dilation and dysfunction may be present but are not necessary for the diagnosis. Evidence: PCS. Frequency: 1/2. (PMID:29478781)
- 3-Methylglutaconic aciduria (HP:0003535): An increased amount of 3-methylglutaconic acid in the urine. Evidence: PCS. Frequency: 2/2. (PMID:29478781)
These phenotypes are associated with the disease mitochondrial complex V (ATP synthase) deficiency, nuclear type 5 (OMIM:618120).