Diseases & Conditions


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Cytochrome C Oxidase Deficiency


Synonyms of Cytochrome C Oxidase Deficiency
  • Complex IV Deficiency
  • COX Deficiency
  • Deficiency of Mitochondrial Respiratory Chain Complex IV

Disorder Subdivisions

  • COX Deficiency French-Canadian Type
  • COX Deficiency Type Benign Infantile Mitochondrial Myopathy
  • COX Def., Infantile Mitochondrial Myopathy, de To ni-Fanconi-Debre included
  • Leigh's Syndrome (Subacute Necrotizing Encephalomyelopathy)


General Discussion
Cytochrome C Oxidase Deficiency is a very rare inherited metabolic disorder characterized by deficiency of the enzyme cytochrome C oxidase (COX), or Complex IV, an essential enzyme that is active in the subcellular structures that help to regulate energy production (mitochondria). Deficiency of COX may be limited (localized) to the tissues of the skeletal muscles or may affect several tissues, such as the heart, kidney, liver, brain, and/or connective tissue (fibroblasts); in other cases, the COX deficiency may be generalized (systemic).

Four distinct forms of Cytochrome C Oxidase Deficiency have been identifed. The first form of this disorder is known as COX Deficiency Type Benign Infantile Mitochondrial Myopathy. Affected infants exhibit many of the same symptoms as those with the more severe infantile form of the disease; however, because the COX deficiency is limited (localized) to tissues of the skeletal muscles, they typically do not have heart or kidney dysfunction.

In the second type of the disease, known as COX Deficiency Type Infantile Mitochondrial Myopathy, because the COX deficiency affects tissues of the skeletal muscles as well as several other tissues, the disorder may be characterized by a generalized weakness of skeletal muscles (myotonia), abnormalities of the heart and kidneys, and/or abnormally high levels of lactic acid in the blood (lactic acidosis).

The third form of COX Deficiency, known as Leigh's Disease (Subacute Necrotizing Encephalomyelopathy), is thought to be a generalized (systemic) form of COX Deficiency. Leigh's Disease is characterized by progressive degeneration of the brain and dysfunction of other organs of the body including the heart, kidneys, muscles, and liver. Symptoms may include loss of previously acquired motor skills, loss of appetite, vomiting, irritability, and/or seizure activity. As Leigh's Disease progresses, symptoms may also include generalized weakness; loss of muscle tone (hypotonia); and/or episodes of lactic acidosis.

In the fourth form of COX Deficiency, known as COX Deficiency French-Canadian Type, the COX deficiency affects tissues of the skeletal muscles, connective tissue, and, in particular, the brain (Leigh's Disease) and the liver. Affected infants and children may demonstrate developmental delays, diminished muscle tone (hypotonia), crossing of the eyes (strabismus), Leigh's Disease, and/or episodes of lactic acidosis.

Many cases of COX Deficiency are inherited as an autosomal recessive genetic trait. However, it is possible that other cases may be inherited due to abnormal changes in genetic material (mutation) found within mitochondria (mtDNA).

Organizations related to Cytochrome C Oxidase Deficiency
  • CLIMB (Children Living with Inherited Metabolic Diseases)
    Climb Building
    Crewe Intl CW2 6BG
    Phone #: +44- 87-0 7700 325
    800 #: --
    e-mail: info@climb.org.uk
    Home page: http://www.CLIMB.org.uk
  • Lactic Acidosis Support Trust
    1A Whitley Close
    Cheshire None CW10 0NQ
    Phone #: 016-068-3719
    800 #: --
    e-mail: N/A
    Home page: N/A
  • MUMS (Mothers United for Moral Support, Inc) National Parent-to-Parent Network
    150 Custer Court
    Green Bay WI 54301-1243
    Phone #: 920-336-5333
    800 #: 877-336-5333
    e-mail: mums@netnet.net
    Home page: http://www.netnet.net/mums/
  • NIH/National Institute of Diabetes, Digestive & Kidney Diseases
    Endocrine Diseases Metabolic Diseases Branch
    Bethesda MD 20892-3570
    Phone #: 301-654-3810
    800 #: --
    e-mail: NDDIC@info.niddk.nih.gov
    Home page: http://www.niddk.nih.gov
  • United Mitochondrial Disease Foundation
    8085 Saltsburg Road
    Pittsburgh PA 15239
    Phone #: 412-793-8077
    800 #: --
    e-mail: info@umdf.org
    Home page: http://www.umdf.org



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc. ? (NORD). A copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see http://www.rarediseases.org/search/rdblist.html