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Genetic and Rare Diseases Information Center (GARD)

Mitochondrial complex III deficiency

Other Names for this Disease
  • Complex 3 mitochondrial respiratory chain deficiency
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What are the signs and symptoms of Mitochondrial complex III deficiency?

The signs and symptoms of mitochondrial complex III deficiency are not the same for each affected individual, because a person with mitochondrial disease can have a unique mixture of healthy and defective mitochondria, with a unique distribution in the body.[1] Several forms of mitochondrial complex III deficiency have been identified, and they are generally grouped based on the age of onset, nature and severity of symptoms.

The most severe form begins in infancy and causes life-threatening muscle and nervous system dysfunction (encephalomyopathy), lactic acidosis at birth, hypotonia (poor muscle tone), dystrophic posturing, seizures, and coma. Ragged-red fibers, a characteristic microscopic abnormality observed in muscle biopsy, are commonly present with this form.[2]

In some individuals, encephalomyopathy does not begin until childhood or adulthood. For these individuals, symptoms may include various combinations of weakness, short stature, ataxia (inability to coordinate muscle movements), dementia, hearing loss, sensory neuropathy, pigmentary retinopathy (a disorder of the retina characterized by deposits of pigment and vision loss), and possible lactic acidosis or other features. Ragged-red fibers are common in these individuals as well.[2]

Individuals with a less severe type may have myopathy with exercise intolerance that progresses to general weakness. Ragged-red fibers and lactic acidosis may be present.[2]

A fourth described form is characterized by infantile histiocytoid cardiomyopathy.[2] This is a condition characterized by cardiomegaly (enlarged heart), severe cardiac arrhythmias or sudden death, and the presence of histiocyte-like cells within the heart muscle.[3]

Last updated: 8/29/2011

The Human Phenotype Ontology provides the following list of signs and symptoms for Mitochondrial complex III deficiency. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms.

Signs and Symptoms Approximate number of patients (when available)
Hearing impairment 5%
Abnormality of the abdominal wall -
Abnormality of the coagulation cascade -
Aminoaciduria -
Ataxia -
Autosomal recessive inheritance -
Brittle hair -
Cataract -
Cerebellar atrophy -
Cerebral atrophy -
Cholangitis -
Cholestasis -
Decreased liver function -
Decreased mitochondrial complex III activity in liver tissue -
Depression -
EEG abnormality -
Elevated hepatic transaminases -
Emotional lability -
Exercise intolerance -
Failure to thrive -
Feeding difficulties in infancy -
Hallucinations -
Hyperreflexia -
Hypertrophic cardiomyopathy -
Hypoglycemia -
Increased serum lactate -
Infantile onset -
Intellectual disability -
Lactic acidosis -
Metabolic acidosis -
Microvesicular hepatic steatosis -
Mitochondrial encephalopathy -
Mitochondrial inheritance -
Muscle weakness -
Muscular hypotonia -
Ragged-red muscle fibers -
Rhabdomyolysis -
Rod-cone dystrophy -
Seizures -
Spasticity -
Tubulointerstitial nephritis -

Last updated: 7/1/2016

The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature.

The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined.

Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.

  1. Facts About Mitochondrial Myopathies. Muscular Dystrophy Association. April 2010; Accessed 4/4/2011.
  2. Types of Mitochondrial Disease. United Mitochondrial Disease Foundation. Accessed 4/4/2011.
  3. Histiocytoid cardiomyopathy. Orphanet. May 2008; Accessed 8/29/2011.

Other Names for this Disease
  • Complex 3 mitochondrial respiratory chain deficiency
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.