Mitochondrial complex III deficiency
- Complex 3 mitochondrial respiratory chain deficiency
- Isolated coenzyme Q-cytochrome C reductase deficiency
- Isolated CoQ-cytochrome C reductase deficiency
- Isolated mitochondrial respiratory chain complex III deficiency
- Isolated ubiquinone-cytochrome C reductase deficiency
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.
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.
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.
A fourth described form is characterized by infantile histiocytoid cardiomyopathy. 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.
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.
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.
- Facts About Mitochondrial Myopathies. Muscular Dystrophy Association. April 2010; http://www.mdausa.org/publications/mitochondrial_myopathies.html#whatare. Accessed 4/4/2011.
- Types of Mitochondrial Disease. United Mitochondrial Disease Foundation. http://www.umdf.org/site/c.otJVJ7MMIqE/b.5692881/k.4B7B/Types_of_Mitochondrial_Disease.htm#Complex3. Accessed 4/4/2011.
- Histiocytoid cardiomyopathy. Orphanet. May 2008; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=137675. Accessed 8/29/2011.