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Last updated: June 28, 2018
Years published: 1997, 1998, 1999, 2007, 2009, 2012, 2015, 2018
NORD gratefully acknowledges George T Griffing, MD, Professor of Medicine, St Louis University School of Medicine, for assistance in the preparation of this report.
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, 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, 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). De Toni-Fanconi-Debre syndrome may also be present and may include excessive thirst, excessive urination, and excessive excretion of glucose, phosphates, amino acids, bicarbonate, calcium and water in the urine.
The third form of COX deficiency, known as Leighโs disease (subacute necrotizing encephalomyelopathy), is thought to be a generalized (systemic) form of COX deficiency. Leighโs 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 Leighโs 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 (Leighโs disease) and the liver. Affected infants and children may demonstrate developmental delays, diminished muscle tone (hypotonia), crossing of the eyes (strabismus), Leighโs disease, and/or episodes of lactic acidosis. Most cases of COX deficiency are inherited in an autosomal recessive pattern. Rarely, COX deficiency occurs as the result of a new or inherited abnormality (mutation) in a mitochondrial gene.
Cytochrome C Oxidase (COX) deficiency is a very rare inherited metabolic disorder characterized by a deficiency of the enzyme cytochrome C oxidase or Complex IV. Cytochrome C oxidase is an essential enzyme that is active in subcellular structures that help to regulate energy production (mitochondria). Four distinct forms of Cytochrome C Oxidase deficiency have been identified. The range and severity of symptoms varies greatly from case to case.
In the first form of this disorder, known as COX deficiency type benign infantile mitochondrial myopathy, deficiency of cytochrome C oxidase may be limited (localized) to the tissues of the skeletal muscles. Therefore, although affected infants may exhibit many of the same symptoms as those associated with the severe infantile form of the disease, the heart and kidneys are not affected. Affected infants with this form of the disorder may experience episodes characterized by the presence of abnormally high levels of lactic acid in the blood (lactic acidosis). If untreated, life-threatening complications (e.g., respiratory failure) may occur. With appropriate, intensive treatment, recovery from this form of COX deficiency may occur spontaneously within the first few years of life.
In the second form of the disorder, COX deficiency type infantile mitochondrial myopathy, deficiency of cytochrome C oxidase affects tissues of the skeletal muscles as well as several other tissues, such as the heart, kidney, liver, brain, and/or connective tissue (fibroblasts). Symptoms associated with this form of the disease typically begin within the first three to four weeks of life. Such symptoms may include generalized muscle weakness as well as heart problems (cardiomyopathy) and kidney dysfunction. Affected infants may also fail to gain weight at the expected rate (failure to thrive) and/or exhibit a weak cry; difficulties sucking, swallowing, and/or breathing; and/or โfloppinessโ or poor muscle tone (hypotonia). In addition, infants with COX deficiency may experience episodes of lactic acidosis, possibly leading to impairment of respiratory and kidney function. Other symptoms may result from a specific defect in the kidneys that leads to de Toni-Fanconi-Debre syndrome, a condition that causes kidney dysfunction and involves excessive urinary excretion of glucose, phosphates, amino acids, bicarbonate, calcium, and water. Symptoms due to de Toni-Fanconi-Debre syndrome may include excessive thirst (polydipsia) and excessive urination (polyuria).
Leighโs disease, also known as subacute necrotizing encephalomyelopathy, is thought to be a generalized (systemic) form of COX deficiency. This form of the disorder is characterized by progressive degeneration of the brain and dysfunction of other organs of the body including the heart, kidneys, muscles, and/or liver. Symptoms generally begin between three months and two years of age. The most predominant symptoms of Leighโs disease involve the brain and spinal cord (central nervous system). In most affected infants, the first noticeable signs may include loss of previously acquired motor skills or loss of head control and poor sucking ability. These symptoms may be accompanied by a profound loss of appetite, vomiting, irritability, continuous crying, and/or possible seizure activity. If the onset is later in childhood (i.e., 2 years), affected children may experience difficulty articulating words (dysarthria) and coordinating voluntary movements such as walking or running (ataxia). Previously acquired intellectual skills may diminish and mental retardation may also occur. (For more complete details on this disorder, please see NORDโs disease report on Leighโs disease. To obtain this information, choose โLeighโ as your search term in the Rare Disease Database.)
In the fourth form of COX deficiency, known as COX deficiency French-Canadian type, deficiency of cytochrome C oxidase affects tissues of the skeletal muscles, connective tissue (fibroblasts), and, in particular, tissues of the brain (Leighโs disease) and liver. However, tissues of the kidney and heart demonstrate near normal cytochrome C oxidase activity. Affected infants and children may demonstrate developmental delays, diminished muscle tone (hypotonia), slight facial abnormalities (mild facial dysmorphism), Leighโs disease, crossing of the eyes (strabismus), impaired ability to control voluntary movements (ataxia), fatty accumulation within and degeneration of the liver (microvesicular steatosis), and/or episodes of lactic acidosis, which may lead to life-threatening complications such as respiratory and kidney failure.
Researchers believe that most cases of Cytochrome C Oxidase deficiency are inherited in an autosomal recessive pattern. (For example, research seems to indicate that COX deficiency French-Canadian type has a recessive mode of inheritance.) Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother.
Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.
All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
Rarely, COX deficiency occurs as the result of a new or inherited mutation in a mitochondrial gene. Mitochondria, found by the hundreds within most cells of the body, regulate the production of cellular energy and carry the genetic blueprints for this process within their own unique DNA. The enzyme cytochrome C oxidase is comprised of 13 subunits, three of which are thought to be encoded by the mitochondrial DNA (mtDNA), while the remaining subunits are encoded by the DNA of the nucleus.
Mutations affecting the genes for mitochondria (mtDNA) are inherited from the mother. MtDNA that is found in sperm cells is typically lost during fertilization. As a result, all human mtDNA comes from the mother. An affected mother will pass on the mutation to all her children, but only her daughters will pass on the mutation to their children. Some affected individuals have a new mtDNA mutation that was not inherited.
As cells divide, the number of normal mtDNA and mutated mtDNA are distributed in an unpredictable fashion among different tissues. Consequently, mutated mtDNA accumulates at different rates among different tissues in the same individual. Thus, family members who have the identical mutation in mtDNA may exhibit a variety of different symptoms and signs at different times and to varying degrees of severity.
Cytochrome C Oxidase (COX) Deficiency is a very rare metabolic disorder that appears to affect males and females in equal numbers. The overall incidence rates of various forms of the disorder (i.e., infantile mitochondrial myopathic forms and Leighโs disease) are unclear. However, COX deficiency French-Canadian type has been reported in the French-Canadian population of the Saguenay-Lac-Saint-Jean region of northeastern Quebec with an estimated incidence of 1 in 2,473 births.
In most cases of the infantile mitochondrial myopathic forms of this disorder, onset occurs within the first month of life. Leighโs disease usually becomes apparent between three months and two years of age. COX deficiency French-Canadian type also tends to become apparent during infancy or childhood. However, in some rare cases, symptoms of COX deficiency may not develop until adolescence or adulthood.
Cytochrome C Oxidase (COX) deficiency may be diagnosed after birth (postnatally) based upon a thorough clinical evaluation, characteristic findings, a detailed patient history, and a variety of specialized tests. According to the medical literature, a diagnosis of COX deficiency should be considered in infants or children who exhibit episodes of lactic acidosis.
Specialized laboratory studies may be performed to help confirm such a diagnosis including enzyme tests (assays) of connective tissue cells (fibroblasts) that may reveal reduced activity of the cytochrome C oxidase enzyme. In addition, muscle biopsy studies may reveal โragged-red fibersโ (a striking, unique abnormality of muscle tissue that is apparent when viewed under a microscope) that demonstrate markedly reduced levels of COX activity as well as alterations or abnormalities of the mitochondrial structure. Other laboratory tests may include specialized staining techniques that reveal which subunits of the COX enzyme are affected.
In infants with COX deficiency type infantile mitochondrial myopathy who also exhibit de Toni-Fanconi-Debre syndrome, laboratory studies may reveal signs of kidney dysfunction including abnormally high levels of glucose, phosphates, amino acids, bicarbonate, calcium, and water in the blood.
The diagnosis of the Leighโs disease form of COX deficiency may be aided by advanced imaging techniques. Computerized tomography (CT) scanning or magnetic resonance imaging (MRI) of the brain may reveal abnormalities of certain areas of the brain (e.g., the brain stem, cerebellum, basal ganglia). During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of the brainโs tissue structure. During MRI, a magnetic field and radio waves are used to create cross-sectional images of the brain. In addition, laboratory studies may reveal a generalized reduction of cytochrome C oxidase enzyme activity within tissues cells of the brain, skeletal muscle, connective tissue (fibroblasts), heart, liver, and kidneys. Laboratory tests may also demonstrate high levels of acidic waste products in the blood (lactic acidosis).
In individuals with COX deficiency French-Canadian type, laboratory studies and advanced imaging tests may reveal findings characteristic of the Leighโs disease form of COX deficiency. In addition, enzyme assays may demonstrate that the severity of reduced cytochrome C oxidase enzyme activity varies greatly in various tissue cells. For example, whereas assays may reveal almost normal levels of COX activity in the heart and kidneys, COX enzyme activity may be approximately 50 percent of normal within skeletal muscle and connective tissue cells (fibroblasts) and severely reduced in brain and liver tissue cells. In addition, imaging studies or other tests may reveal abnormal fatty accumulation within and degeneration of the liver (microvesicular steatosis).
Molecular genetic testing is available to identify some of the nuclear and mitochondrial gene mutations associated with COX deficiency.
Treatment
Treatment of all forms of COX deficiency is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists who may need to systematically and comprehensively plan an affected childโs treatments. Such specialists may include pediatricians; physicians who diagnose and treat abnormalities of the kidneys (nephrologists), musculoskeletal system (orthopedists), heart (cardiologists), lungs (pulmonologists), nervous system (neurologists), and/or liver (hepatologists); and/or other health care professionals. In the case of benign infantile mitochondrial myopathy, it is important that early diagnosis and intensive treatment be pursued until spontaneous recovery is realized.
Genetic counseling is recommended for affected individuals and their families. Other treatment is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]
Some current clinical trials also are posted on the following page on the NORD website:
https://rarediseases.org/living-with-a-rare-disease/find-clinical-trials/
For information about clinical trials sponsored by private sources, contact:
www.centerwatch.com
For information about clinical trials conducted in Europe, contact:
https://www.clinicaltrialsregister.eu/
Cytochrome C Oxidase Deficiency Resources
(Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder [e.g., lactic acidosis].)
TEXTBOOKS
Bennett JC, Plum F, eds. Cecil Textbook of Medicine, 20th ed. W.B. Saunders Co.;1996:2167.
Behrman RE, ed.; Nelson Textbook of Pediatrics, 15th Ed. W.B. Saunders Company;1996:1754.
Lyon G, et al., eds. Neurology of Hereditary Metabolic Diseases in Childhood, 2nd Ed. McGraw-Hill;1996:27.
Scriver CR, et al., eds. The Metabolic and Molecular Bases of Inherited Disease, 7th Ed. McGraw-Hill, Inc.;1995:1537-38,1615-16.
Buyse ML, editor-in-chief. Birth Defects Encyclopedia. Blackwell Scientific Publications;1990:1202-03.
JOURNAL ARTICLES
Vogt, Sebastian, Volker Ruppert, Sabine Pankuweit, Jรลพrgen pj Paletta, and Petra Weber. Reduced Cytochrome C Oxidase Subunit Iv in Patients with Dilated Cardiomyopathy. Exp Clin Card 2014;20: 1009-1028.
Huฬttemann M, Klewer S, Lee I, Pecinova A, Pecina P, Liu J, Lee M, Doan JW, Larson D, Slack E, Maghsoodi B, Erickson RP, Grossman LI, Mice deleted for heart-type cytochrome c oxidase subunit 7a1 develop dilated cardiomyopathy. Mitochondrion 2012;12:294-304.
Huigsloot M, Nijtmans LG, Szklarczyk R, Baars MJ, van den Brand MA, Hendriksfranssen MG, van den Heuvel LP, Smeitink JA, Huynen MA, Rodenburg RJ, A mutation in C2orf64 causes impaired cytochrome c oxidase assembly and mitochondrial cardiomyopathy. Am J Hum Genet. 2011;88:488-9.
Vogt S, Portig I, Irqsusi M, Ruppert V, Weber P, Ramzan R, Heat shock protein expression and change of cytochrome c oxidase activity: presence of two phylogenic old systems to protect tissues in ischemia and reperfusion. J Bioenerg Biomembr 2011;43:425-35.
Arbustini E, Diegoli M, Fasani R, et al.. Mitochondrial DNA mutations and mitochondrial abnormalities in dilated cardiomyopathy. Am J Pathol 1998;153:1501-1510.
DiMauro S, et al. Cytochrome C oxidase deficiency. Pediatr Res. 1990;28(5):536-41.
Von Kleist-Retzow JC, et al. A high rate (20% โ 30%) of parental consanguinity in cytochrome-oxidase deficiency. Am J Hum Genet. 1998;63(2):428-35.
Isobe K, et al. Nuclear-recessive mutations of factors involved in mitochondrial translation are responsible for age-related respiration deficiency of human skin fibroblasts. J Biol Chem. 1998;273(8):4601-06.
Possekel S, et al. Immunohistochemical analysis of muscle cytochrome C oxidase deficiency in children. Histochem Cell Biol. 1995;103(1):59-68.
Tiranti V, et al. Nuclear DNA origin of cytochrome C oxidase deficiency in Leighโs syndrome: genetic evidence based on patientโs-derived RHO degrees transformants. Hum Mol Genet. 1995;4(11):2017-23.
Saunier P, et al. Cytochrome C oxidase deficiency presenting as recurrent neonatal myoglobinuria. Neuromuscul Disord. 1995;5(4):285-89.
Morin C, et al. Clinical, metabolic, and genetic aspects of cytochrome C oxidase deficiency in Saguenay-Lac-Saint-Jean. Am J Hum Genet. 1993;53(2):488-96.
Merante F, et al. A biochemically distinct form of cytochrome oxidase (COX) deficiency in the Saguenay-Lac-Saint-Jean region of Quebec. Am J Hum Genet. 1993;53(2):481-87.
DiMauro S, et al. Mitochondrial encephalomyopathies. Arch Neurol.1993;50(11):1197-208.
Salo MK, et al. Reversible mitochondrial myopathy with cytochrome C oxidase deficiency. Arch Dis Child. 1992;67(8):1033-35.
Keppler K, et al. Variable presentation of cytochrome C oxidase deficiency. Am J Dis Child. 1992;146(11):1349-52.
Eshel G, et al. Autosomal recessive lethal infantile cytochrome C deficiency. Am J Dis Child. 1991;145(6):661-64.
Lutz R et al.An atypical case of cytochrome C oxidase deficiency with biochemical heterogeneity in fibroblasts. Neurology. 1991;41(12):1957-60.
Lombes A, et al. Biochemical and molecular analysis of cytochrome C oxidase deficiency in Leighโs syndrome. Neurology. 1991;41(4):491-98.
Tritschler HJ, et al. Differential diagnosis of fatal and benign cytochrome C oxidase-deficient myopathies of infancy: an immunohistochemical approach. Neurology. 1991;41(2 Pt 1):300-05.
Adamovich K, et al. Cytochrome C oxidase deficiency. Orv Hetil. 1990;131(32):1761-63.
Buchwald A, Till H, Unterberg C, Oberschmidt R, et al. Alterations of the mitochondrial respiratory chain in human dilated cardiomyopathy. Eur Heart J 1990; 11:509- 516.
Nozaki H, et al. Cytochrome C oxidase deficiency with acute onset and rapid recovery. Pediatr Neurol. 1990;6(5):330-32.
INTERNET
McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. Entry Number: 220110 https://omim.org/entry/220110 ; Last Update: 09/08/2017 and Entry Number: 220111 https://omim.org/entry/220111; Last Edit Date: 03/15/2018. Accessed June 28, 2018.
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Learn more https://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORDโs mission.
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Learn more https://rarediseases.org/patient-assistance-programs/caregiver-respite/The information provided on this page is for informational purposes only. The National Organization for Rare Disorders (NORD) does not endorse the information presented. The content has been gathered in partnership with the MONDO Disease Ontology. Please consult with a healthcare professional for medical advice and treatment.
The Genetic and Rare Diseases Information Center (GARD) has information and resources for patients, caregivers, and families that may be helpful before and after diagnosis of this condition. GARD is a program of the National Center for Advancing Translational Sciences (NCATS), part of the National Institutes of Health (NIH).
View reportOrphanet has a summary about this condition that may include information on the diagnosis, care, and treatment as well as other resources. Some of the information and resources are available in languages other than English. The summary may include medical terms, so we encourage you to share and discuss this information with your doctor. Orphanet is the French National Institute for Health and Medical Research and the Health Programme of the European Union.
View reportOnline Mendelian Inheritance In Man (OMIM) has a summary of published research about this condition and includes references from the medical literature. The summary contains medical and scientific terms, so we encourage you to share and discuss this information with your doctor. OMIM is authored and edited at the McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine.
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