- Progressive (HP:0003676): Applies to a disease manifestation that increases in scope or severity over the course of time, i.e., that worsens with age. Evidence: PCS. (PMID:25512002)
- Increased circulating pyruvate concentration (HP:0003542): The concentration of pyruvate in the blood circulation is above the upper limit of normal. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
- Dysmetria (HP:0001310): A type of ataxia characterized by the inability to carry out movements with the correct range and motion across the plane of more than one joint related to incorrect estimation of the distances required for targeted movements. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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: PCS. Frequency: 1/1. (PMID:25512002)
- Focal impaired awareness seizure (HP:0002384): Focal impaired awareness seizure (or focal seizure with impaired or lost awareness) is a type of focal-onset seizure characterized by some degree (which may be partial) of impairment of the person's awareness of themselves or their surroundings at any point during the seizure. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- Dysarthria (HP:0001260): Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
- Gowers sign (HP:0003391): A phenomenon whereby patients are not able to stand up without the use of the hands owing to weakness of the proximal muscles of the lower limbs. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- Fatigue (HP:0012378): A subjective feeling of tiredness characterized by a lack of energy and motivation. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
- Decreased CSF 5-methyltetrahydrofolate concentration (HP:0012446): A reduced concentration of 5-methyltetrahydrofolate(2-) in the cerebrospinal fluid (CSF). 5-methyltetrahydrofolate is the active folate metabolite. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- Childhood onset (HP:0011463): Onset of disease at the age of between 1 and 5 years. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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:25512002)
- Tip-toe gait (HP:0030051): An abnormal gait pattern characterized by the failure of the heel to contact the floor at the onset of stance during gait. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- Mitochondrial myopathy (HP:0003737): A type of myopathy associated with mitochondrial disease and characterized by findings on biopsy such as ragged red muscle fibers. Evidence: PCS. (PMID:25512002)
- Proximal muscle weakness (HP:0003701): A lack of strength of the proximal muscles. Evidence: PCS. Frequency: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
- 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: 1/1. (PMID:25512002)
These phenotypes are associated with the disease mitochondrial myopathy-lactic acidosis-deafness syndrome (OMIM:251950).