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Mitochondrial complex 4 deficiency, nuclear type 7(MC4DN7)

MedGen UID:
1754683
Concept ID:
C5436685
Disease or Syndrome
Synonym: MITOCHONDRIAL COMPLEX IV DEFICIENCY, NUCLEAR TYPE 7
 
Gene (location): COX6B1 (19q13.12)
 
Monarch Initiative: MONDO:0033637
OMIM®: 619051

Definition

Mitochondrial complex IV deficiency nuclear type 7 (MC4DN7) is an autosomal recessive metabolic encephalomyopathic disorder with highly variable manifestations. Only a few patients have been reported. Some patients have normal early development then show rapid neurodegeneration with progressive muscle weakness, gait disturbances, and cognitive decline in mid to late childhood. Other features may include seizures and visual impairment. Brain imaging shows progressive leukodystrophy with cystic lesions. In contrast, at least 1 patient has been reported who presented in the neonatal period with metabolic acidosis, hydrocephalus, hypotonia, and cortical blindness. This patient developed hypertrophic cardiomyopathy resulting in early death. All patients had increased serum lactate and decreased levels and activity of mitochondrial respiratory complex IV (summary by Massa et al., 2008 and Abdulhag et al., 2015). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110. [from OMIM]

Clinical features

From HPO
Myalgia
MedGen UID:
68541
Concept ID:
C0231528
Sign or Symptom
Pain in muscle.
Hypertrophic cardiomyopathy
MedGen UID:
2881
Concept ID:
C0007194
Disease or Syndrome
Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality.
Cardiomegaly
MedGen UID:
5459
Concept ID:
C0018800
Finding
Increased size of the heart, clinically defined as an increased transverse diameter of the cardiac silhouette that is greater than or equal to 50% of the transverse diameter of the chest (increased cardiothoracic ratio) on a posterior-anterior projection of a chest radiograph or a computed tomography.
Tricuspid regurgitation
MedGen UID:
11911
Concept ID:
C0040961
Disease or Syndrome
Failure of the tricuspid valve to close sufficiently upon contraction of the right ventricle, causing blood to regurgitate (flow backward) into the right atrium.
Ventricular hypertrophy
MedGen UID:
87400
Concept ID:
C0340279
Disease or Syndrome
Enlargement of the cardiac ventricular muscle tissue with increase in the width of the wall of the ventricle and loss of elasticity. Ventricular hypertrophy is clinically differentiated into left and right ventricular hypertrophy.
Pulmonary arterial hypertension
MedGen UID:
425404
Concept ID:
C2973725
Disease or Syndrome
Pulmonary hypertension is defined mean pulmonary artery pressure of 25mmHg or more and pulmonary capillary wedge pressure of 15mmHg or less when measured by right heart catheterisation at rest and in a supine position.
Fetal growth restriction
MedGen UID:
4693
Concept ID:
C0015934
Pathologic Function
An abnormal restriction of fetal growth with fetal weight below the tenth percentile for gestational age.
Feeding difficulties
MedGen UID:
65429
Concept ID:
C0232466
Finding
Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Leukodystrophy
MedGen UID:
6070
Concept ID:
C0023520
Disease or Syndrome
Leukodystrophy refers to deterioration of white matter of the brain resulting from degeneration of myelin sheaths in the CNS. Their basic defect is directly related to the synthesis and maintenance of myelin membranes. Symmetric white matter involvement at MRI is a typical finding in patients with leukodystrophies.
Mental deterioration
MedGen UID:
66713
Concept ID:
C0234985
Mental or Behavioral Dysfunction
Loss of previously present mental abilities, generally in adults.
Truncal ataxia
MedGen UID:
96535
Concept ID:
C0427190
Sign or Symptom
Truncal ataxia is a sign of ataxia characterized by instability of the trunk. It usually occurs during sitting.
Limb ataxia
MedGen UID:
196692
Concept ID:
C0750937
Finding
A kind of ataxia that affects movements of the extremities.
Increased CSF lactate
MedGen UID:
257904
Concept ID:
C1167918
Finding
Increased concentration of lactate in the cerebrospinal fluid.
Undetectable visual evoked potentials
MedGen UID:
376697
Concept ID:
C1850069
Finding
Ventriculomegaly
MedGen UID:
480553
Concept ID:
C3278923
Finding
An increase in size of the ventricular system of the brain.
Muscle weakness
MedGen UID:
57735
Concept ID:
C0151786
Finding
Reduced strength of muscles.
Generalized hypotonia
MedGen UID:
346841
Concept ID:
C1858120
Finding
Generalized muscular hypotonia (abnormally low muscle tone).
Cytochrome C oxidase-negative muscle fibers
MedGen UID:
867360
Concept ID:
C4021724
Finding
An abnormally reduced activity of the enzyme cytochrome C oxidase in muscle tissue.
Lactic acidosis
MedGen UID:
1717
Concept ID:
C0001125
Disease or Syndrome
An abnormal buildup of lactic acid in the body, leading to acidification of the blood and other bodily fluids.
Metabolic acidosis
MedGen UID:
65117
Concept ID:
C0220981
Pathologic Function
Metabolic acidosis (MA) is characterized by a fall in blood pH due to a reduction of serum bicarbonate concentration. This can occur as a result of either the accumulation of acids (high anion gap MA) or the loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic MA). By definition, MA is not due to a respirary cause.
Hyperketonemia
MedGen UID:
66722
Concept ID:
C0235430
Disease or Syndrome
An increase in the level of ketone bodies (acetoacetic acid, beta-hydroxybutyric acid, and acetone) in the blood.
Hyper-beta-alaninemia
MedGen UID:
75702
Concept ID:
C0268630
Disease or Syndrome
An increased concentration of alanine in the blood.
Increased circulating lactate concentration
MedGen UID:
332209
Concept ID:
C1836440
Finding
Abnormally increased level of blood lactate (2-hydroxypropanoic acid). Lactate is produced from pyruvate by lactate dehydrogenase during normal metabolism. The terms lactate and lactic acid are often used interchangeably but lactate (the component measured in blood) is strictly a weak base whereas lactic acid is the corresponding acid. Lactic acidosis is often used clinically to describe elevated lactate but should be reserved for cases where there is a corresponding acidosis (pH below 7.35).
Hyperammonemia
MedGen UID:
1802066
Concept ID:
C5574662
Laboratory or Test Result
An increased concentration of ammonia in the blood.
Visual loss
MedGen UID:
784038
Concept ID:
C3665386
Finding
Loss of visual acuity (implying that vision was better at a certain time point in life). Otherwise the term reduced visual acuity should be used (or a subclass of that).
Cerebral visual impairment
MedGen UID:
890568
Concept ID:
C4048268
Pathologic Function
A form of loss of vision caused by damage to the visual cortex rather than a defect in the eye.

Recent clinical studies

Etiology

Salminen A, Kaarniranta K, Kauppinen A, Ojala J, Haapasalo A, Soininen H, Hiltunen M
Prog Neurobiol 2013 Jul-Aug;106-107:33-54. Epub 2013 Jul 1 doi: 10.1016/j.pneurobio.2013.06.002. PMID: 23827971

Diagnosis

Garone C, D'Souza AR, Dallabona C, Lodi T, Rebelo-Guiomar P, Rorbach J, Donati MA, Procopio E, Montomoli M, Guerrini R, Zeviani M, Calvo SE, Mootha VK, DiMauro S, Ferrero I, Minczuk M
Hum Mol Genet 2017 Nov 1;26(21):4257-4266. doi: 10.1093/hmg/ddx314. PMID: 28973171Free PMC Article
Hallmann K, Kudin AP, Zsurka G, Kornblum C, Reimann J, Stüve B, Waltz S, Hattingen E, Thiele H, Nürnberg P, Rüb C, Voos W, Kopatz J, Neumann H, Kunz WS
Brain 2016 Feb;139(Pt 2):338-45. Epub 2015 Dec 17 doi: 10.1093/brain/awv357. PMID: 26685157

Prognosis

Hallmann K, Kudin AP, Zsurka G, Kornblum C, Reimann J, Stüve B, Waltz S, Hattingen E, Thiele H, Nürnberg P, Rüb C, Voos W, Kopatz J, Neumann H, Kunz WS
Brain 2016 Feb;139(Pt 2):338-45. Epub 2015 Dec 17 doi: 10.1093/brain/awv357. PMID: 26685157

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