- Dementia (HP:0000726): A loss of global cognitive ability of sufficient amount to interfere with normal social or occupational function. Dementia represents a loss of previously present cognitive abilities, generally in adults, and can affect memory, thinking, language, judgment, and behavior. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- 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. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Muscle weakness (HP:0001324): Reduced strength of muscles. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Migraine (HP:0002076): Migraine is a chronic neurological disorder characterized by episodic attacks of headache and associated symptoms. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- 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: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- EEG abnormality (HP:0002353): Abnormality observed by electroencephalogram (EEG), which is used to record of the brain's spontaneous electrical activity from multiple electrodes placed on the scalp. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Aphasia (HP:0002381): An acquired language impairment of some or all of the abilities to produce or comprehend speech and to read or write. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Stroke-like episode (HP:0002401): No consensus exists on what a stroke-like episode is, but these episodes can be functionally defined as a new neurological deficit, occurring with or without the context of seizures, which last longer than 24 hours. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Lactic acidosis (HP:0003128): An abnormal buildup of lactic acid in the body, leading to acidification of the blood and other bodily fluids. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Ragged-red muscle fibers (HP:0003200): An abnormal appearance of muscle fibers observed on muscle biopsy. Ragged red fibers can be visualized with Gomori trichrome staining as irregular and intensely red subsarcolemmal zones, whereas the normal myofibrils are green. The margins of affect fibers appear red and ragged. The ragged-red is due to the accumulation of abnormal mitochondria below the plasma membrane of the muscle fiber, leading to the appearance of a red rim and speckled sarcoplasm. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Abnormal mitochondria in muscle tissue (HP:0008316): An abnormality of the mitochondria in muscle tissue. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Aplasia/Hypoplasia of the cerebral white matter (HP:0012429): Absence or underdevelopment of the cerebral white matter. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Widened cerebral subarachnoid space (HP:0012766): An increase in size of the anatomic space between the arachnoid membrane and pia mater in the region surrounding the cerebrum. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:550)
- Sensorineural hearing impairment (HP:0000407): A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Visual loss (HP:0000572): Loss of visual acuity (implying that vision was better at a certain time point in life). Otherwise the term reduced visual acuity should be used (or a subclass of that). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Psychosis (HP:0000709): A condition characterized by changes in personality and thought patterns, often accompanied by hallucinations and delusional beliefs, is known as psychosis. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Depression (HP:0000716): Frequently experiencing feelings of being down, miserable, and/or hopeless; struggling to recover from these moods; having a pessimistic outlook on the future; feeling a pervasive sense of shame; having a low self-worth; experiencing thoughts of suicide and engaging in suicidal behavior. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Short attention span (HP:0000736): Reduced attention span characterized by distractibility and impulsivity. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Anxiety (HP:0000739): Intense feelings of nervousness, tension, or panic often arise in response to interpersonal stresses. There is worry about the negative effects of past unpleasant experiences and future negative possibilities. Individuals may feel fearful, apprehensive, or threatened by uncertainty, and they may also have fears of falling apart or losing control. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Diabetes mellitus (HP:0000819): A group of abnormalities characterized by hyperglycemia and glucose intolerance. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Ataxia (HP:0001251): 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Hemiparesis (HP:0001269): Loss of strength in the arm, leg, and sometimes face on one side of the body. Hemiplegia refers to a complete loss of strength, whereas hemiparesis refers to an incomplete loss of strength. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Gait disturbance (HP:0001288): The term gait disturbance can refer to any disruption of the ability to walk. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Specific learning disability (HP:0001328): Impairment of certain skills such as reading or writing, coordination, self-control, or attention that interfere with the ability to learn. The impairment is not related to a global deficiency of intelligence. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Myoclonus (HP:0001336): Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Vomiting (HP:0002013): Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Basal ganglia calcification (HP:0002135): The presence of calcium deposition affecting one or more structures of the basal ganglia. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Recurrent paroxysmal headache (HP:0002331): Repeated episodes of headache with rapid onset, reaching a peak within minutes and of short duration (less than one hour) with pain that is throbbing, pulsating, or bursting in quality. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Memory impairment (HP:0002354): An impairment of memory as manifested by a reduced ability to remember things such as dates and names, and increased forgetfulness. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Increased CSF lactate (HP:0002490): Increased concentration of lactate in the cerebrospinal fluid. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Increased CSF protein concentration (HP:0002922): Increased concentration of protein in the cerebrospinal fluid. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Myopathy (HP:0003198): A disorder of muscle unrelated to impairment of innervation or neuromuscular junction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Fluctuations in consciousness (HP:0007159): Changes in one's level of awareness and responsiveness to their environment. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Focal-onset seizure (HP:0007359): A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- 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: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Impaired visuospatial constructive cognition (HP:0010794): Reduced ability affecting mainly visuospatial cognition which may be tested using pattern construction (for example by Differential Ability Scales, which test a person's strengths and weaknesses across a range of intellectual abilities). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:550)
- Proteinuria (HP:0000093): Increased levels of protein in the urine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Focal segmental glomerulosclerosis (HP:0000097): Segmental accumulation of scar tissue in individual (but not all) glomeruli. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Nephropathy (HP:0000112): A nonspecific term referring to disease or damage of the kidneys. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Proximal tubulopathy (HP:0000114): Dysfunction of the proximal tubule, which is the portion of the duct system of the nephron of the kidney which leads from Bowman's capsule to the loop of Henle. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Pigmentary retinopathy (HP:0000580): An abnormality of the retina characterized by pigment deposition. It is typically associated with migration and proliferation of macrophages or retinal pigment epithelial cells into the retina; melanin from these cells causes the pigmentary changes. Pigmentary retinopathy is a common final pathway of many retinal conditions and is often associated with visual loss. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Progressive external ophthalmoplegia (HP:0000590): Initial bilateral ptosis followed by limitation of eye movements in all directions and slowing of saccades. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Optic atrophy (HP:0000648): Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Personality changes (HP:0000751): An abnormal shift in patterns of thinking, acting, or feeling. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Hypertrichosis (HP:0000998): Hypertrichosis is increased hair growth that is abnormal in quantity or location. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Vitiligo (HP:0001045). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Agenesis of corpus callosum (HP:0001274): Absence of the corpus callosum as a result of the failure of the corpus callosum to develop, which can be the result of a failure in any one of the multiple steps of callosal development including cellular proliferation and migration, axonal growth or glial patterning at the midline. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Psychotic mentation (HP:0001345): A pattern of thinking and perceiving characterized by a loss of contact with reality, leading to significant changes in thoughts, perceptions, and behaviors. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Failure to thrive (HP:0001508): Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Cardiomyopathy (HP:0001638): A myocardial disorder in which the heart muscle is structurally and functionally abnormal, in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease sufficient to cause the observed myocardial abnormality. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Wolff-Parkinson-White syndrome (HP:0001716): A disorder of the cardiac conduction system of the heart characterized by ventricular preexcitation due to the presence of an abnormal accessory atrioventricular electrical conduction pathway. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Anemia (HP:0001903): A reduction in erythrocytes volume or hemoglobin concentration. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Fever (HP:0001945): Body temperature elevated above the normal range. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Diarrhea (HP:0002014): Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Constipation (HP:0002019): Infrequent or difficult evacuation of feces. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Pulmonary arterial hypertension (HP:0002092): Pulmonary hypertension is defined mean pulmonary artery pressure of 25mmHg or more and pulmonary capillary wedge pressure of 15mmHg or less when measured by right heart catheterisation at rest and in a supine position. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Cerebral cortical atrophy (HP:0002120): Atrophy of the cortex of the cerebrum. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Gastrointestinal dysmotility (HP:0002579): Abnormal intestinal contractions, such as spasms and intestinal paralysis, related to the loss of the ability of the gut to coordinate muscular activity because of endogenous or exogenous causes. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Peripheral axonal neuropathy (HP:0003477): An abnormality characterized by disruption of the normal functioning of peripheral axons. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- 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: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Reduced consciousness (HP:0004372): Abnormally diminished level of attention, responsiveness, or wakefulness. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Intestinal pseudo-obstruction (HP:0004389): A functional rather than mechanical obstruction of the intestines, associated with manifestations that resemble those caused by an intestinal obstruction, including distension, abdominal pain, nausea, vomiting, constipation or diarrhea, in an individual in whom a mechanical blockage has been excluded. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Concentric hypertrophic cardiomyopathy (HP:0005157): Hypertrophic cardiomyopathy with an symmetrical and concentric pattern of hypertrophy. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Type II diabetes mellitus (HP:0005978): A type of diabetes mellitus initially characterized by insulin resistance and hyperinsulinemia and subsequently by glucose interolerance and hyperglycemia. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Distal peripheral sensory neuropathy (HP:0007067): Peripheral sensory neuropathy affecting primarily distal sensation. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Sensorimotor neuropathy (HP:0007141). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Bipolar affective disorder (HP:0007302): Bipolar disorder is an illness of mood characterized by alternating episodes of elevated and depressed moods, which are interspersed with euthymic periods. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Mixed demyelinating and axonal polyneuropathy (HP:0007327). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Erythema (HP:0010783): Redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Abnormal central motor function (HP:0011442): An anomaly of the control or production of movement in the central nervous system. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Brain atrophy (HP:0012444): Partial or complete wasting (loss) of brain tissue that was once present. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Elevated brain lactate level by MRS (HP:0012707): An increase in the level of lactate in the brain identified by magnetic resonance spectroscopy (MRS). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Stuttering (HP:0025268): Disruptions in the production of speech sounds, with involuntary repetitions of words or parts of words, prolongations of speech sounds, or complete blockage of speech production for several seconds. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Cardiac conduction abnormality (HP:0031546): Any anomaly of the progression of electrical impulses through the heart. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Recurrent pancreatitis (HP:0100027): A recurrent form of pancreatitis. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Type I diabetes mellitus (HP:0100651): A chronic condition in which the pancreas produces little or no insulin. Type I diabetes mellitus is manifested by the sudden onset of severe hyperglycemia with rapid progression to diabetic ketoacidosis unless treated with insulin. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:550)
- Hypogonadotropic hypogonadism (HP:0000044): Hypogonadotropic hypogonadism is characterized by reduced function of the gonads (testes in males or ovaries in females) and results from the absence of the gonadal stimulating pituitary hormones: follicle stimulating hormone (FSH) and luteinizing hormone (LH). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:550)
- Hypothyroidism (HP:0000821): Deficiency of thyroid hormone. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:550)
- Hypoparathyroidism (HP:0000829): A condition caused by a deficiency of parathyroid hormone characterized by hypocalcemia and hyperphosphatemia. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:550)
These phenotypes are associated with the disease MELAS (ORPHA:550).