- Poor speech (HP:0002465). Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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: 1/2. (PMID:26189817)
- Difficulty standing (HP:0003698). Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Delayed CNS myelination (HP:0002188): Delayed myelination in the central nervous system. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Malabsorption (HP:0002024): Impaired ability to absorb one or more nutrients from the intestine. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Narrow mouth (HP:0000160): Distance between the commissures of the mouth more than 2 SD below the mean. Alternatively, an apparently decreased width of the oral aperture (subjective). Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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: PCS. Frequency: 1/2. (PMID:26189817)
- Glycosuria (HP:0003076): An increased concentration of glucose in the urine. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Cirrhosis (HP:0001394): A chronic disorder of the liver in which liver tissue becomes scarred and is partially replaced by regenerative nodules and fibrotic tissue resulting in loss of liver function. Evidence: PCS. Frequency: 2/2. (PMID:26189817)
- Brain atrophy (HP:0012444): Partial or complete wasting (loss) of brain tissue that was once present. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Failure to thrive (HP:0001508): Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Irritability (HP:0000737): An emotional state characterized by negative feelings of heightened frustration, annoyance, or feeling upset, often triggered by internal factors (e.g., fatigue, hunger, unfulfilled desires) or external factors (e.g., social or environmental challenges). Irritability may be unpredictable, and is accompanied by a lowered threshold for emotional reactivity and observable features (speech, facial expressions, or psychomotor activity). Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Young adult onset (HP:0011462): Onset of disease at the age of between 16 and 40 years. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: PCS. Frequency: 2/2. (PMID:26189817)
- Elevated hemoglobin A1c (HP:0040217): An increased concentration of hemoglobin A1c (HbA1c), which is the product of nonenzymatic attachment of a hexose molecule to the N-terminal amino acid of the hemoglobin molecule. This reaction is dependent on blood glucose concentration, and therefore reflects the mean glucose concentration over the previous 8 to 12 weeks. The HbA1c level provides a better indication of long-term glycemic control than one-time blood or urinary glucose measurements. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Cytochrome C oxidase-negative muscle fibers (HP:0003688): An abnormally reduced activity of the enzyme cytochrome C oxidase in muscle tissue. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Nausea and vomiting (HP:0002017): Nausea is a commonly encountered symptom that has been defined as an unpleasant painless subjective feeling that one will imminently vomit. Vomiting has been defined as the forceful expulsion of the contents of the stomach, duodenum, or jejunum through the oral cavity. While nausea and vomiting are often thought to exist on a temporal continuum, this is not always the case. There are situations when severe nausea may be present without emesis and less frequently, when emesis may be present without preceding nausea. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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: 2/2. (PMID:26189817)
- Hyperreflexia (HP:0001347): Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Exertional dyspnea (HP:0002875): Perceived difficulty to breathe that occurs with exercise or exertion and improves with rest. Evidence: PCS. Frequency: 2/2. (PMID:26189817)
- 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:26189817)
- Neonatal onset (HP:0003623): Onset of signs or symptoms of disease within the first 28 days of life. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Babinski sign (HP:0003487): Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Feeding difficulties (HP:0011968): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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: 1/2. (PMID:26189817)
- 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:26189817)
- 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. Frequency: 1/2. (PMID:26189817)
- Blue sclerae (HP:0000592): An abnormal bluish coloration of the sclera. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Dyspnea (HP:0002094): Difficult or labored breathing. Dyspnea is a subjective feeling only the patient can rate, e.g., on a Borg scale. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 2-3 toe syndactyly (HP:0004691): Syndactyly with fusion of toes two and three. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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: 1/2. (PMID:26189817)
- Hypertrophic cardiomyopathy (HP:0001639): Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Exocrine pancreatic insufficiency (HP:0001738): Impaired function of the exocrine pancreas associated with a reduced ability to digest foods because of lack of digestive enzymes. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Peripheral neuropathy (HP:0009830): Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- 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:26189817)
- 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: 1/2. (PMID:26189817)
- 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: PCS. Frequency: 2/2. (PMID:26189817)
- Renal tubular dysfunction (HP:0000124): Abnormal function of the renal tubule. The basic functional unit of the kidney, the nephron, consists of a renal corpuscle attached to a renal tubule, with roughly 0.8 to 1.5 nephrons per adult kidney. The functions of the renal tubule include reabsorption of water, electrolytes, glucose, and amino acids and secretion of substances such as uric acid. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Triangular face (HP:0000325): Facial contour, as viewed from the front, triangular in shape, with breadth at the temples and tapering to a narrow chin. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Tremor (HP:0001337): An unintentional, oscillating to-and-fro muscle movement about a joint axis. Evidence: PCS. Frequency: 1/2. (PMID:26189817)
- Glucose intolerance (HP:0001952): Glucose intolerance (GI) can be defined as dysglycemia that comprises both prediabetes and diabetes. It includes the conditions of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) and diabetes mellitus (DM). Evidence: PCS. Frequency: 1/2. (PMID:26189817)
These phenotypes are associated with the disease combined oxidative phosphorylation defect type 26 (OMIM:616539).