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Mitochondrial DNA depletion syndrome 6 (hepatocerebral type)(NN; NNH; MTDPS6)

MedGen UID:
338045
Concept ID:
C1850406
Disease or Syndrome
Synonyms: Mitochondrial DNA depletion syndrome type 6; Navajo neurohepatopathy; Navajo neuropathy
SNOMED CT: Navajo neuropathy (784346006); Navajo neurohepatopathy (784346006)
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): MPV17 (2p23.3)
 
Monarch Initiative: MONDO:0009747
OMIM®: 256810
Orphanet: ORPHA255229

Definition

MPV17-related mitochondrial DNA (mtDNA) maintenance defect presents in the vast majority of affected individuals as an early-onset encephalohepatopathic (hepatocerebral) disease that is typically associated with mtDNA depletion, particularly in the liver. A later-onset neuromyopathic disease characterized by myopathy and neuropathy, and associated with multiple mtDNA deletions in muscle, has also rarely been described. MPV17-related mtDNA maintenance defect, encephalohepatopathic form is characterized by: Hepatic manifestations (liver dysfunction that typically progresses to liver failure, cholestasis, hepatomegaly, and steatosis); Neurologic involvement (developmental delay, hypotonia, microcephaly, and motor and sensory peripheral neuropathy); Gastrointestinal manifestations (gastrointestinal dysmotility, feeding difficulties, and failure to thrive); and Metabolic derangements (lactic acidosis and hypoglycemia). Less frequent manifestations include renal tubulopathy, nephrocalcinosis, and hypoparathyroidism. Progressive liver disease often leads to death in infancy or early childhood. Hepatocellular carcinoma has been reported. [from GeneReviews]

Additional descriptions

From OMIM
Mitochondrial DNA depletion syndrome-6 is an autosomal recessive disorder characterized by infantile onset of progressive liver failure, often leading to death in the first year of life. Those that survive develop progressive neurologic involvement, including ataxia, hypotonia, dystonia, and psychomotor regression (Spinazzola et al., 2008). For a discussion of genetic heterogeneity of autosomal recessive mtDNA depletion syndromes, see MTDPS1 (603041).  http://www.omim.org/entry/256810
From MedlinePlus Genetics
MPV17-related hepatocerebral mitochondrial DNA depletion syndrome is an inherited disorder that can cause liver disease and neurological problems. The signs and symptoms of this condition begin in infancy and typically include vomiting, diarrhea, and an inability to grow or gain weight at the expected rate (failure to thrive). Many affected infants have a buildup of a chemical called lactic acid in the body (lactic acidosis) and low blood glucose (hypoglycemia). Within the first weeks of life, infants develop liver disease that quickly progresses to liver failure. The liver is frequently enlarged (hepatomegaly) and liver cells often have a reduced ability to release a digestive fluid called bile (cholestasis). Rarely, affected children develop liver cancer. After the onset of liver disease, many affected infants develop neurological problems, which can include developmental delay, weak muscle tone (hypotonia), and reduced sensation in the limbs (peripheral neuropathy). Individuals with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome typically survive only into infancy or early childhood.

MPV17-related hepatocerebral mitochondrial DNA depletion syndrome is most frequently seen in the Navajo population of the southwestern United States. In this population, the condition is known as Navajo neurohepatopathy. People with Navajo neurohepatopathy tend to have a longer life expectancy than those with MPV17-related hepatocerebral mitochondrial DNA depletion syndrome. In addition to the signs and symptoms described above, people with Navajo neurohepatopathy may have problems with sensing pain that can lead to painless bone fractures and self-mutilation of the fingers or toes. Individuals with Navajo neurohepatopathy may lack feeling in the clear front covering of the eye (corneal anesthesia), which can lead to open sores and scarring on the cornea, resulting in impaired vision. The cause of these additional features is unknown.  https://medlineplus.gov/genetics/condition/mpv17-related-hepatocerebral-mitochondrial-dna-depletion-syndrome

Clinical features

From HPO
Autoamputation of digits
MedGen UID:
343770
Concept ID:
C1852289
Finding
The spontaneous detachment of a digit (finger or toe) from the body due to long standing pathology.
Short stature
MedGen UID:
87607
Concept ID:
C0349588
Finding
A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).
Growth delay
MedGen UID:
99124
Concept ID:
C0456070
Pathologic Function
A deficiency or slowing down of growth pre- and postnatally.
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.
Abdominal distention
MedGen UID:
34
Concept ID:
C0000731
Finding
Distention of the abdomen.
Ascites
MedGen UID:
416
Concept ID:
C0003962
Disease or Syndrome
Accumulation of fluid in the peritoneal cavity.
Cholestasis
MedGen UID:
925
Concept ID:
C0008370
Disease or Syndrome
Impairment of bile flow due to obstruction in bile ducts.
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.
Hepatomegaly
MedGen UID:
42428
Concept ID:
C0019209
Finding
Abnormally increased size of the liver.
Jaundice
MedGen UID:
43987
Concept ID:
C0022346
Sign or Symptom
Yellow pigmentation of the skin due to bilirubin, which in turn is the result of increased bilirubin concentration in the bloodstream.
Cirrhosis of liver
MedGen UID:
7368
Concept ID:
C0023890
Disease or Syndrome
A chronic disorder of the liver in which liver tissue becomes scarred and is partially replaced by regenerative nodules and fibrotic tissue resulting in loss of liver function.
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.
Liver failure
MedGen UID:
88444
Concept ID:
C0085605
Disease or Syndrome
A disorder characterized by the inability of the liver to metabolize chemicals in the body. Causes include cirrhosis and drug-induced hepatotoxicity. Signs and symptoms include jaundice and encephalopathy. Laboratory test results reveal abnormal plasma levels of ammonia, bilirubin, lactic dehydrogenase, and alkaline phosphatase.
Acute liver failure
MedGen UID:
58125
Concept ID:
C0162557
Disease or Syndrome
Hepatic failure refers to the inability of the liver to perform its normal synthetic and metabolic functions, which can result in coagulopathy and alteration in the mental status of a previously healthy individual. Hepatic failure is defined as acute if there is onset of encephalopathy within 8 weeks of the onset of symptoms in a patient with a previously healthy liver.
Micronodular cirrhosis
MedGen UID:
75640
Concept ID:
C0267812
Disease or Syndrome
A type of cirrhosis characterized by the presence of small regenerative nodules.
Macrovesicular hepatic steatosis
MedGen UID:
373290
Concept ID:
C1837256
Finding
A form of hepatic steatosis characterized by the presence of large, lipid-laden vesicles in the affected hepatocytes.
Reye syndrome-like episodes
MedGen UID:
340530
Concept ID:
C1850413
Finding
Repeated occurrences of acute noninflammatory encephalopathy and fatty degenerative liver failure.
Microvesicular hepatic steatosis
MedGen UID:
376784
Concept ID:
C1850415
Finding
A form of hepatic steatosis characterized by the presence of small, lipid-laden vesicles in the affected hepatocytes.
Hepatocellular necrosis
MedGen UID:
343247
Concept ID:
C1855038
Disease or Syndrome
Prolonged neonatal jaundice
MedGen UID:
347108
Concept ID:
C1859236
Finding
Neonatal jaundice refers to a yellowing of the skin and other tissues of a newborn infant as a result of increased concentrations of bilirubin in the blood. Neonatal jaundice affects over half of all newborns to some extent in the first week of life. Prolonged neonatal jaundice is said to be present if the jaundice persists for longer than 14 days in term infants and 21 days in preterm infants.
Hepatocellular carcinoma
MedGen UID:
389187
Concept ID:
C2239176
Neoplastic Process
Hepatocellular carcinoma is the major histologic type of malignant primary liver neoplasm. It is the fifth most common cancer and the third most common cause of death from cancer worldwide. The major risk factors for HCC are chronic hepatitis B virus (HBV) infection, chronic hepatitis C virus (HCV) infection, prolonged dietary aflatoxin exposure, alcoholic cirrhosis, and cirrhosis due to other causes. Hepatoblastomas comprise 1 to 2% of all malignant neoplasms of childhood, most often occurring in children under 3 years of age. Hepatoblastomas are thought to be derived from undifferentiated hepatocytes (Taniguchi et al., 2002).
Hepatic steatosis
MedGen UID:
398225
Concept ID:
C2711227
Disease or Syndrome
Steatosis is a term used to denote lipid accumulation within hepatocytes.
Cerebellar ataxia
MedGen UID:
849
Concept ID:
C0007758
Disease or Syndrome
Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).
Dystonic disorder
MedGen UID:
3940
Concept ID:
C0013421
Sign or Symptom
An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.
Peripheral neuropathy
MedGen UID:
18386
Concept ID:
C0031117
Disease or Syndrome
Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Pain insensitivity
MedGen UID:
488855
Concept ID:
C0344307
Finding
Inability to perceive painful stimuli.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Hyporeflexia
MedGen UID:
195967
Concept ID:
C0700078
Finding
Reduction of neurologic reflexes such as the knee-jerk reaction.
Broad-based gait
MedGen UID:
167799
Concept ID:
C0856863
Finding
An abnormal gait pattern in which persons stand and walk with their feet spaced widely apart. This is often a component of cerebellar ataxia.
Sensorimotor neuropathy
MedGen UID:
207266
Concept ID:
C1112256
Disease or Syndrome
Loss of ambulation
MedGen UID:
332305
Concept ID:
C1836843
Finding
Inability to walk in a person who previous had the ability to walk.
Painless fractures due to injury
MedGen UID:
325208
Concept ID:
C1837602
Finding
An increased tendency to fractures following trauma, with fractures occurring without pain.
Distal sensory impairment
MedGen UID:
335722
Concept ID:
C1847584
Finding
An abnormal reduction in sensation in the distal portions of the extremities.
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Decreased number of peripheral myelinated nerve fibers
MedGen UID:
346872
Concept ID:
C1858285
Finding
A loss of myelinated nerve fibers in the peripheral nervous system (in general, this finding can be observed on nerve biopsy).
Diffuse leukoencephalopathy
MedGen UID:
358229
Concept ID:
C1868514
Finding
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.
Progressive muscle weakness
MedGen UID:
68704
Concept ID:
C0240421
Finding
Corneal scarring
MedGen UID:
83899
Concept ID:
C0349702
Finding
Replacement of corneal tissue with scar tissue as a result of injury to the deeper layers of the cornea.
Distal muscle weakness
MedGen UID:
140883
Concept ID:
C0427065
Finding
Reduced strength of the musculature of the distal extremities.
Muscular atrophy
MedGen UID:
892680
Concept ID:
C0541794
Pathologic Function
The presence of skeletal muscular atrophy (which is also known as amyotrophy).
Increased susceptibility to fractures
MedGen UID:
234655
Concept ID:
C1390474
Finding
An abnormally increased tendency to fractures of bones caused by an abnormal reduction in bone strength that is generally associated with an increased risk of fracture.
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.
Osteomyelitis leading to amputation due to slow healing fractures
MedGen UID:
351263
Concept ID:
C1864975
Finding
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.
Hypoglycemia
MedGen UID:
6979
Concept ID:
C0020615
Disease or Syndrome
A decreased concentration of glucose in the blood.
Elevated circulating aspartate aminotransferase concentration
MedGen UID:
57497
Concept ID:
C0151904
Finding
The concentration of aspartate aminotransferase (AST) in the blood circulation is above the upper limit of normal.
Elevated circulating alanine aminotransferase concentration
MedGen UID:
57740
Concept ID:
C0151905
Finding
An abnormally high concentration in the circulation of alanine aminotransferase (ALT).
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.
Recurrent hypoglycemia
MedGen UID:
335382
Concept ID:
C1846288
Finding
Recurrent episodes of decreased concentration of glucose in the blood.
Elevated gamma-glutamyltransferase level
MedGen UID:
1370086
Concept ID:
C4476869
Finding
Increased level of the enzyme gamma-glutamyltransferase (GGT). GGT is mainly present in kidney, liver, and pancreatic cells, but small amounts are present in other tissues.
Acral ulceration
MedGen UID:
1648438
Concept ID:
C4732740
Finding
A type of digital ulcer that manifests as an open sore on the surface of the skin at the tip of a finger or toe.
Corneal ulceration
MedGen UID:
40486
Concept ID:
C0010043
Disease or Syndrome
Disruption of the epithelial layer of the cornea with involvement of the underlying stroma.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Recurrent corneal erosions
MedGen UID:
56353
Concept ID:
C0155119
Disease or Syndrome
The presence of recurrent corneal epithelial erosions. Although most corneal epithelial defects heal quickly, some may show recurrent ulcerations.
Decreased activity of mitochondrial complex I
MedGen UID:
393796
Concept ID:
C2677650
Finding
A reduction in the activity of the mitochondrial respiratory chain complex I, which is part of the electron transport chain in mitochondria.
Decreased activity of mitochondrial complex III
MedGen UID:
460434
Concept ID:
C3149083
Finding
A reduction in the activity of the mitochondrial respiratory chain complex III, which is part of the electron transport chain in mitochondria.
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 6 (hepatocerebral type) in Orphanet.

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