- Dystonia (HP:0001332, a Human Phenotype Ontology term): 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:24367056)
- Seizure (HP:0001250, a Human Phenotype Ontology term): 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:24367056)
- Left ventricular systolic dysfunction (HP:0025169, a Human Phenotype Ontology term): Abnormality of left ventricular contraction, often defined operationally as an ejection fraction of less than 40 percent. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Hypotonia (HP:0001252, a Human Phenotype Ontology term): 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:24367056)
- Ataxia (HP:0001251, a Human Phenotype Ontology term): Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly). Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Reduced brain N-acetyl aspartate level by MRS (HP:0012708, a Human Phenotype Ontology term): A decrease in the level of N-acetyl aspartate in the brain identified by magnetic resonance spectroscopy (MRS). Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Hepatomegaly (HP:0002240, a Human Phenotype Ontology term): Abnormally increased size of the liver. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Infantile onset (HP:0003593, a Human Phenotype Ontology term): Onset of signs or symptoms of disease between 28 days to one year of life. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Aspiration pneumonia (HP:0011951, a Human Phenotype Ontology term): Pneumonia due to the aspiration (breathing in) of food, liquid, or gastric contents into the upper respiratory tract. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Ketonuria (HP:0002919, a Human Phenotype Ontology term): High levels of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the urine. Ketone bodies are insignificant in the blood and urine of normal individuals in the postprandial or overnight-fasted state. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Fetal onset (HP:0011461, a Human Phenotype Ontology term): Onset prior to birth but after 8 weeks of embryonic development (corresponding to a gestational age of 10 weeks). Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Lacticaciduria (HP:0003648, a Human Phenotype Ontology term): An increased concentration of lactic acid in the urine. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Decreased activity of mitochondrial complex II (HP:0008314, a Human Phenotype Ontology term): A reduction in the activity of the mitochondrial respiratory chain complex II, which is part of the electron transport chain in mitochondria. Evidence: PCS. Frequency: 2/2. (PMID:26008905;PMID:24367056)
- Lactic acidosis (HP:0003128, a Human Phenotype Ontology term): 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:24367056)
- Dilated cardiomyopathy (HP:0001644, a Human Phenotype Ontology term): 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: 1/1. (PMID:26008905)
- Developmental regression (HP:0002376, a Human Phenotype Ontology term): Loss of developmental skills, as manifested by loss of developmental milestones. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Feeding difficulties (HP:0011968, a Human Phenotype Ontology term): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Global developmental delay (HP:0001263, a Human Phenotype Ontology term): 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: 1/1. (PMID:24367056)
- Secondary microcephaly (HP:0005484, a Human Phenotype Ontology term): Head circumference which falls below 2 standard deviations below the mean for age and gender because of insufficient head growth after birth. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Left ventricular noncompaction (HP:0030682, a Human Phenotype Ontology term): Left ventricular noncompaction (LVNC) is defined by 3 markers: prominent left ventricular (LV) trabeculae, deep intertrabecular recesses, and the thin compacted layer. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Tricuspid regurgitation (HP:0005180, a Human Phenotype Ontology term): Failure of the tricuspid valve to close sufficiently upon contraction of the right ventricle, causing blood to regurgitate (flow backward) into the right atrium. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Pendular nystagmus (HP:0012043, a Human Phenotype Ontology term): Rhythmic, involuntary sinusoidal oscillations of one or both eyes. The waveform of pendular nystagmus may occur in any direction. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Autosomal recessive inheritance (HP:0000007, a Human Phenotype Ontology term): 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:24367056)
- Left ventricular hypertrophy (HP:0001712, a Human Phenotype Ontology term): Enlargement or increased size of the heart left ventricle. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Visual impairment (HP:0000505, a Human Phenotype Ontology term): Visual impairment (or vision impairment) is vision loss (of a person) to such a degree as to qualify as an additional support need through a significant limitation of visual capability resulting from either disease, trauma, or congenital or degenerative conditions that cannot be corrected by conventional means, such as refractive correction, medication, or surgery. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Optic disc pallor (HP:0000543, a Human Phenotype Ontology term): A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Neonatal death (HP:0003811, a Human Phenotype Ontology term): Death within the first 28 days of life. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Mitral regurgitation (HP:0001653, a Human Phenotype Ontology term): An abnormality of the mitral valve characterized by insufficiency or incompetence of the mitral valve resulting in retrograde leaking of blood through the mitral valve upon ventricular contraction. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
- Myoclonus (HP:0001336, a Human Phenotype Ontology term): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: PCS. Frequency: 1/1. (PMID:24367056)
- Patent foramen ovale (HP:0001655, a Human Phenotype Ontology term): Failure of the foramen ovale to seal postnatally, leaving a potential conduit between the left and right cardiac atria. Evidence: PCS. Frequency: 1/1. (PMID:26008905)
These phenotypes are associated with the disease mitochondrial complex 2 deficiency, nuclear type 3 (OMIM:619167, an entry in Online Mendelian Inheritance in Man).