Traits

Traits linked to MDH2

malate dehydrogenase 2

The Human Phenotype Ontology links 84 traits to MDH2, by body system: features seen in people with one of the gene's rare conditions.

Abnormality of the nervous system

Trait	How often it is seen
Absent speech development	Always
Delayed ability to crawl	Always
Delayed ability to sit	Always
Epilepsy	Always
Global developmental delay	Always
Abnormal pyramidal sign	Often (30–79%)
Babinski sign	Often (30–79%)
Corpus callosum atrophy	Often (30–79%)
Decrease in size of the outer layer of the brain due to loss of brain cells	Often (30–79%)
Decreased reflex response	Often (30–79%)
Degeneration of cerebellum	Often (30–79%)
Delayed CNS myelination	Often (30–79%)
Disorder of involuntary muscle movements	Often (30–79%)
Dystonia	Often (30–79%)
Epileptic spasm	Often (30–79%)
Episodic paroxysmal anxiety	Often (30–79%)
Generalized tonic seizure	Often (30–79%)
Myoclonic seizure	Often (30–79%)
Poor eye contact	Often (30–79%)
Recurrent paroxysmal headache	Often (30–79%)
Seizure affecting one half of brain	Often (30–79%)
Cranial nerve compression	Sometimes (5–29%)
Inability to move vocal cords	Sometimes (5–29%)
Panic attack	Sometimes (5–29%)
Tremor	Sometimes (5–29%)
Epileptic encephalopathy	Not recorded
Inability to walk	Not recorded

Abnormality of the cardiovascular system

Trait	How often it is seen
Decrease in blood pressure upon standing up	Often (30–79%)
Fainting spell	Often (30–79%)
High blood pressure	Often (30–79%)
Hypertension associated with pheochromocytoma	Often (30–79%)
Hypertensive retinopathy	Often (30–79%)
Palpitations	Often (30–79%)
Positive regitine blocking test	Often (30–79%)
Sinus tachycardia	Often (30–79%)
Arachnoid hemangiomatosis	Sometimes (5–29%)
Cardiac failure	Sometimes (5–29%)
Disease of the heart muscle	Sometimes (5–29%)
Hypertensive crisis	Sometimes (5–29%)
Inflammation of heart muscle	Sometimes (5–29%)

Laboratory abnormality

Trait	How often it is seen
Elevated lactate:pyruvate ratio	Always
Higher than normal levels of lactate in blood	Always
Increased CSF lactate	Always
Elevated urinary dopamine	Often (30–79%)
Elevated urinary epinephrine level	Often (30–79%)
Elevated urinary norepinephrine level	Often (30–79%)
High blood calcium levels	Often (30–79%)
High urine protein levels	Often (30–79%)
Blood in urine	Sometimes (5–29%)
Elevated calcitonin	Sometimes (5–29%)
High blood sugar	Sometimes (5–29%)

Abnormality of the digestive system

Trait	How often it is seen
Constipation	Often (30–79%)
Intermittent abdominal pain	Often (30–79%)
Nausea	Often (30–79%)
Abdominal mass	Sometimes (5–29%)
Feeding difficulties	Not recorded

Abnormality of the endocrine system

Trait	How often it is seen
Adrenal pheochromocytoma	Very often (80–99%)
Extraadrenal pheochromocytoma	Very often (80–99%)
Paraganglioma	Very often (80–99%)
Paraganglioma of head and neck	Often (30–79%)

Abnormality of the musculoskeletal system

Trait	How often it is seen
Low muscle tone	Always
Muscle weakness	Always
Poor head control	Always
Muscle degeneration	Not recorded

Abnormality of the ear

Trait	How often it is seen
Paroxysmal vertigo	Often (30–79%)
Pulsatile tinnitus	Often (30–79%)
Conductive deafness	Sometimes (5–29%)

Abnormality of the eye

Trait	How often it is seen
Cross-eyed	Often (30–79%)
Rod-cone dystrophy	Often (30–79%)
Absent iris	Rarely (1–4%)

Abnormality of the genitourinary system

Trait	How often it is seen
Glomerular sclerosis	Often (30–79%)
Cancer starting in small tubes in kidneys	Sometimes (5–29%)
Renal failure	Sometimes (5–29%)

Abnormality of the integument

Trait	How often it is seen
Flushing	Often (30–79%)
Sporadic excessive sweating	Often (30–79%)
Paleness	Sometimes (5–29%)

Constitutional symptom

Trait	How often it is seen
Chest pain	Often (30–79%)
Fatigue	Often (30–79%)

Growth abnormality

Trait	How often it is seen
Faltering weight	Often (30–79%)
Weight loss	Often (30–79%)

Abnormality of blood and blood-forming tissues

Trait	How often it is seen
Bleeding in brain	Often (30–79%)

Abnormality of head or neck

Trait	How often it is seen
Retinal capillary hemangioma	Sometimes (5–29%)

Abnormality of the breast

Trait	How often it is seen
Accessory nipple	Often (30–79%)

Abnormality of the voice

Trait	How often it is seen
Inability to produce voice sounds	Often (30–79%)

How often is among people with one of the gene's conditions, the most often across them, as the Human Phenotype Ontology records it. These pages describe traits and the research behind them; they are not a diagnosis, and a doctor or genetic counsellor is the person to ask about symptoms.

Where this comes from

The Human Phenotype Ontology, release 2026-09-01: the traits linked to MDH2 and how often each is seen. Find out more at hpo.jax.org.

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