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Mitochondrial DNA depletion syndrome 8a(MTDPS8A)

MedGen UID:
412815
Concept ID:
C2749861
Disease or Syndrome
Synonyms: MITOCHONDRIAL DNA DEPLETION SYNDROME 8A (ENCEPHALOMYOPATHIC TYPE WITH RENAL TUBULOPATHY); Mitochondrial DNA depletion syndrome, encephalomyopathic form, with renal tubulopathy; MITOCHONDRIAL DNA DEPLETION SYNDROME, ENCEPHALOMYOPATHIC, WITH RENAL TUBULOPATHY, AUTOSOMAL RECESSIVE
SNOMED CT: Mitochondrial DNA depletion syndrome 8A encephalomyopathic type with renal tubulopathy (765100000); Ribonucleotide reductase regulatory TP53 inducible subunit M2B-related mitochondrial deoxyribonucleic acid depletion syndrome encephalomyopathic form with renal tubulopathy (765100000); RRM2B-related mitochondrial DNA depletion syndrome, encephalomyopathic form with renal tubulopathy (765100000); Mitochondrial DNA depletion syndrome, encephalomyopathic form with renal tubulopathy (765100000)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Gene (location): RRM2B (8q22.3)
 
Monarch Initiative: MONDO:0012792
OMIM®: 612075
Orphanet: ORPHA255235

Disease characteristics

Excerpted from the GeneReview: RRM2B Mitochondrial DNA Maintenance Defects
Four phenotypes comprise the RRM2B mitochondrial DNA maintenance defects (RRM2B-MDMDs): RRM2B encephalomyopathic MDMD, the most severe phenotype, usually manifesting shortly after birth as hypotonia, poor feeding, and faltering growth requiring hospitalization. Subsequent assessments are likely to reveal multisystem involvement including sensorineural hearing loss, renal tubulopathy, and respiratory failure. Autosomal dominant progressive external ophthalmoplegia (adPEO), typically adult onset; other manifestations can include ptosis, bulbar dysfunction, fatigue, and muscle weakness. RRM2B autosomal recessive progressive external ophthalmoplegia (arPEO), a typically childhood-onset predominantly myopathic phenotype of PEO, ptosis, proximal muscle weakness, and bulbar dysfunction. RRM2B mitochondrial neurogastrointestinal encephalopathy (MNGIE)-like, characterized by progressive ptosis, ophthalmoplegia, gastrointestinal dysmotility, cachexia, and peripheral neuropathy. To date, 78 individuals from 52 families with a molecularly confirmed RRM2B-MDMD have been reported. [from GeneReviews]
Authors:
Albert Z Lim  |  Robert McFarland  |  Robert W Taylor, et. al.   view full author information

Additional descriptions

From OMIM
Mitochondrial DNA depletion syndrome-8A is a severe autosomal recessive disorder characterized by neonatal hypotonia, lactic acidosis, and neurologic deterioration. Renal tubular involvement may also occur (Bourdon et al., 2007). Mitochondrial DNA depletion syndrome-8B is characterized by ophthalmoplegia, ptosis, gastrointestinal dysmotility, cachexia, peripheral neuropathy, and brain MRI changes, known as the MNGIE phenotype (Shaibani et al., 2009). For a discussion of genetic heterogeneity of mtDNA depletion syndromes, see MTDPS1 (603041).  http://www.omim.org/entry/612075
From MedlinePlus Genetics
Mitochondrial neurogastrointestinal encephalopathy (MNGIE) disease is a condition that affects several parts of the body, particularly the digestive system and nervous system. The major features of MNGIE disease can appear anytime from infancy to adulthood, but signs and symptoms most often begin by age 20. The medical problems associated with this disorder worsen over time.

Almost all people with MNGIE disease have a condition known as gastrointestinal dysmotility, in which the muscles and nerves of the digestive system do not move food through the digestive tract efficiently. The resulting digestive problems include feelings of fullness (satiety) after eating only a small amount, trouble swallowing (dysphagia), nausea and vomiting after eating, episodes of abdominal pain, diarrhea, and intestinal blockage. These gastrointestinal problems lead to extreme weight loss and reduced muscle mass (cachexia).

MNGIE disease is also characterized by abnormalities of the nervous system, although these tend to be milder than the gastrointestinal problems. Affected individuals experience tingling, numbness, and weakness in their limbs (peripheral neuropathy), particularly in the hands and feet. Additional neurological signs and symptoms can include droopy eyelids (ptosis), weakness of the muscles that control eye movement (ophthalmoplegia), and hearing loss. Leukoencephalopathy, which is the deterioration of a type of brain tissue known as white matter, is a hallmark of MNGIE disease. These changes in the brain can be seen with magnetic resonance imaging (MRI), though they usually do not cause symptoms in people with this disorder.  https://medlineplus.gov/genetics/condition/mitochondrial-neurogastrointestinal-encephalopathy-disease

Clinical features

From HPO
Aminoaciduria
MedGen UID:
116067
Concept ID:
C0238621
Disease or Syndrome
An increased concentration of an amino acid in the urine.
Proximal tubulopathy
MedGen UID:
326534
Concept ID:
C1839603
Disease or Syndrome
Dysfunction of the proximal tubule, which is the portion of the duct system of the nephron of the kidney which leads from Bowman's capsule to the loop of Henle.
Cachexia
MedGen UID:
2773
Concept ID:
C0006625
Sign or Symptom
Severe weight loss, wasting of muscle, loss of appetite, and general debility related to a chronic disease.
Weight loss
MedGen UID:
853198
Concept ID:
C1262477
Finding
Reduction of total body weight.
Failure to thrive
MedGen UID:
746019
Concept ID:
C2315100
Disease or Syndrome
Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.
Diarrhea
MedGen UID:
8360
Concept ID:
C0011991
Sign or Symptom
Abnormally increased frequency (usually defined as three or more) loose or watery bowel movements a day.
Vomiting
MedGen UID:
12124
Concept ID:
C0042963
Sign or Symptom
Forceful ejection of the contents of the stomach through the mouth by means of a series of involuntary spasmic contractions.
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.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterised by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Status epilepticus
MedGen UID:
11586
Concept ID:
C0038220
Disease or Syndrome
Status epilepticus is a type of prolonged seizure resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which lead to abnormally prolonged seizures (after time point t1). It is a condition that can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures.
Gait ataxia
MedGen UID:
155642
Concept ID:
C0751837
Sign or Symptom
A type of ataxia characterized by the impairment of the ability to coordinate the movements required for normal walking. Gait ataxia is characteirzed by a wide-based staggering gait with a tendency to fall.
Increased CSF lactate
MedGen UID:
257904
Concept ID:
C1167918
Finding
Increased concentration of lactate in the cerebrospinal fluid.
Progressive neurologic deterioration
MedGen UID:
381506
Concept ID:
C1854838
Finding
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Subnormal intellectual functioning which originates during the developmental period. Intellectual disability, previously referred to as mental retardation, has been defined as an IQ score below 70.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Axial hypotonia
MedGen UID:
342959
Concept ID:
C1853743
Finding
Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk.
Generalized hypotonia
MedGen UID:
346841
Concept ID:
C1858120
Finding
Generalized muscular hypotonia (abnormally low muscle tone).
Respiratory distress
MedGen UID:
96907
Concept ID:
C0476273
Sign or Symptom
Respiratory distress is objectively observable as the physical or emotional consequences from the experience of dyspnea. The physical presentation of respiratory distress is generally referred to as labored breathing, while the sensation of respiratory distress is called shortness of breath or dyspnea.
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.
Severe lactic acidosis
MedGen UID:
374223
Concept ID:
C1839436
Finding
A severe form of lactic acidemia.
External ophthalmoplegia
MedGen UID:
57662
Concept ID:
C0162292
Disease or Syndrome
Paralysis of the external ocular muscles.
Decreased activity of mitochondrial complex IV
MedGen UID:
866520
Concept ID:
C4020800
Finding
A reduction in the activity of the mitochondrial respiratory chain complex IV, which is part of the electron transport chain in mitochondria.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
Follow this link to review classifications for Mitochondrial DNA depletion syndrome 8a in Orphanet.

Professional guidelines

PubMed

Halter J, Schüpbach W, Casali C, Elhasid R, Fay K, Hammans S, Illa I, Kappeler L, Krähenbühl S, Lehmann T, Mandel H, Marti R, Mattle H, Orchard K, Savage D, Sue CM, Valcarcel D, Gratwohl A, Hirano M
Bone Marrow Transplant 2011 Mar;46(3):330-337. Epub 2010 May 3 doi: 10.1038/bmt.2010.100. PMID: 20436523Free PMC Article
Scarpelli M, Cotelli MS, Mancuso M, Tomelleri G, Tonin P, Baronchelli C, Vielmi V, Gregorelli V, Todeschini A, Padovani A, Filosto M
Recent Pat CNS Drug Discov 2010 Nov;5(3):203-9. doi: 10.2174/157488910793362412. PMID: 20722626

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