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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
Myalgia
MedGen UID:
68541
Concept ID:
C0231528
Sign or Symptom
Pain in muscle.
Exercise intolerance
MedGen UID:
603270
Concept ID:
C0424551
Finding
A functional motor deficit where individuals whose responses to the challenges of exercise fail to achieve levels considered normal for their age and gender.
Nephrocalcinosis
MedGen UID:
10222
Concept ID:
C0027709
Disease or Syndrome
Nephrocalcinosis is the deposition of calcium salts in renal parenchyma.
Secondary amenorrhea
MedGen UID:
115919
Concept ID:
C0232940
Disease or Syndrome
The cessation of menstruation for six months or more in a female that is not pregnant, breastfeeding or menopausal.
Nephrolithiasis
MedGen UID:
98227
Concept ID:
C0392525
Disease or Syndrome
The presence of calculi (stones) in the kidneys.
Dark urine
MedGen UID:
604849
Concept ID:
C0426396
Finding
An abnormal dark color of 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.
Global proximal tubulopathy
MedGen UID:
868445
Concept ID:
C4022839
Disease or Syndrome
A type of proximal renal tubulopathy characterized by resorption defects leading to glycosuria, aminoaciduria, tubular proteinuria, renal hypophosphatemia, and urate tubular hyporeabsorption with bicarbonate loss and resulting acidosis.
Lacticaciduria
MedGen UID:
871116
Concept ID:
C4025585
Finding
An increased concentration of lactic acid in the urine.
Pes planus
MedGen UID:
42034
Concept ID:
C0016202
Anatomical Abnormality
A foot where the longitudinal arch of the foot is in contact with the ground or floor when the individual is standing; or, in a patient lying supine, a foot where the arch is in contact with the surface of a flat board pressed against the sole of the foot by the examiner with a pressure similar to that expected from weight bearing; or, the height of the arch is reduced.
Absent Achilles reflex
MedGen UID:
108240
Concept ID:
C0558845
Finding
Absence of the Achilles reflex (also known as the ankle jerk reflex), which can normally be elicited by tapping the tendon is tapped while the foot is dorsiflexed.
Pes cavus
MedGen UID:
675590
Concept ID:
C0728829
Congenital Abnormality
An increase in height of the medial longitudinal arch of the foot that does not flatten on weight bearing (i.e., a distinctly hollow form of the sole of the foot when it is bearing weight).
Hammertoe
MedGen UID:
209712
Concept ID:
C1136179
Anatomical Abnormality
Hyperextension of the metatarsal-phalangeal joint with hyperflexion of the proximal interphalangeal (PIP) joint.
Weakness of the intrinsic hand muscles
MedGen UID:
322432
Concept ID:
C1834536
Finding
Lower limb muscle weakness
MedGen UID:
324478
Concept ID:
C1836296
Finding
Weakness of the muscles of the legs.
Decreased Achilles reflex
MedGen UID:
324765
Concept ID:
C1837323
Finding
Decreased intensity of the Achilles reflex (also known as the ankle jerk reflex), which can be elicited by tapping the tendon is tapped while the foot is dorsiflexed.
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.
Foot dorsiflexor weakness
MedGen UID:
356163
Concept ID:
C1866141
Finding
Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles.
Claw toe deformity
MedGen UID:
1841785
Concept ID:
C5826373
Anatomical Abnormality
Claw toes are characterized by hyperextension at the metatarsal-phalangeal joints and flexion of the interphalangeal joints.
Bradycardia
MedGen UID:
140901
Concept ID:
C0428977
Finding
A slower than normal heart rate (in adults, slower than 60 beats per minute).
Lower limb asymmetry
MedGen UID:
44089
Concept ID:
C0023221
Finding
A difference in length or diameter between the left and right leg.
Small for gestational age
MedGen UID:
65920
Concept ID:
C0235991
Finding
Smaller than normal size according to sex and gestational age related norms, defined as a weight below the 10th percentile for the gestational age.
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.
Upper limb asymmetry
MedGen UID:
867635
Concept ID:
C4022024
Anatomical Abnormality
Difference in length or size between the right and left arm.
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 (between the layers of the peritoneum that lines the abdomen).
Cholelithiasis
MedGen UID:
3039
Concept ID:
C0008350
Disease or Syndrome
Hard, pebble-like deposits that form within the gallbladder.
Cholestasis
MedGen UID:
925
Concept ID:
C0008370
Disease or Syndrome
Impairment of bile flow due to obstruction in bile ducts.
Intrahepatic cholestasis
MedGen UID:
3042
Concept ID:
C0008372
Disease or Syndrome
Impairment of bile flow due to obstruction in the small bile ducts within the liver.
Constipation
MedGen UID:
1101
Concept ID:
C0009806
Sign or Symptom
Infrequent or difficult evacuation of feces.
Dysphagia
MedGen UID:
41440
Concept ID:
C0011168
Disease or Syndrome
Difficulty in swallowing.
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.
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.
Micronodular cirrhosis
MedGen UID:
75640
Concept ID:
C0267812
Disease or Syndrome
A type of cirrhosis characterized by the presence of small regenerative nodules.
Gastrointestinal dysmotility
MedGen UID:
324638
Concept ID:
C1836923
Finding
Abnormal intestinal contractions, such as spasms and intestinal paralysis, related to the loss of the ability of the gut to coordinate muscular activity because of endogenous or exogenous causes.
Poor suck
MedGen UID:
324693
Concept ID:
C1837142
Finding
An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed.
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.
Episodic vomiting
MedGen UID:
333228
Concept ID:
C1838993
Finding
Paroxysmal, recurrent episodes of vomiting.
Periportal fibrosis
MedGen UID:
337906
Concept ID:
C1849766
Disease or Syndrome
The presence of fibrosis affecting the interlobular stroma of liver.
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.
Depletion of mitochondrial DNA in liver
MedGen UID:
870570
Concept ID:
C4025018
Finding
An abnormal reduction in the number of mitochondria in hepatocytes.
Gastroesophageal reflux
MedGen UID:
1368658
Concept ID:
C4317146
Finding
A condition in which the stomach contents leak backwards from the stomach into the esophagus through the lower esophageal sphincter.
Increased hepatic echogenicity
MedGen UID:
1382460
Concept ID:
C4477000
Finding
Increased echogenicity of liver tissue on sonography, manifested as an increased amount of white on the screen of the sonography device.
Hearing impairment
MedGen UID:
235586
Concept ID:
C1384666
Disease or Syndrome
A decreased magnitude of the sensory perception of sound.
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).
Depression
MedGen UID:
4229
Concept ID:
C0011581
Mental or Behavioral Dysfunction
Frequently experiencing feelings of being down, miserable, and/or hopeless; struggling to recover from these moods; having a pessimistic outlook on the future; feeling a pervasive sense of shame; having a low self-worth; experiencing thoughts of suicide and engaging in suicidal behavior.
Dysarthria
MedGen UID:
8510
Concept ID:
C0013362
Mental or Behavioral Dysfunction
Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.
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.
Fasciculations
MedGen UID:
5124
Concept ID:
C0015644
Sign or Symptom
Fasciculations are observed as small, local, involuntary muscle contractions (twitching) visible under the skin. Fasciculations result from increased irritability of an axon (which in turn is often a manifestation of disease of a motor neuron). This leads to sporadic discharges of all the muscle fibers controlled by the axon in isolation from other motor units.
Periventricular leukomalacia
MedGen UID:
6072
Concept ID:
C0023529
Disease or Syndrome
Periventricular leukomalacia is characterized by diffuse injury of deep cerebral white matter, accompanied in its most severe form by focal necrosis. The neuropathologic hallmarks of PVL are microglial activation and focal and diffuse periventricular depletion of premyelinating oligodendroglia.
Intellectual disability, mild
MedGen UID:
10044
Concept ID:
C0026106
Mental or Behavioral Dysfunction
Mild intellectual disability is defined as an intelligence quotient (IQ) in the range of 50-69.
Intellectual disability, moderate
MedGen UID:
7680
Concept ID:
C0026351
Mental or Behavioral Dysfunction
Moderate mental retardation is defined as an intelligence quotient (IQ) in the range of 35-49.
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.
Intellectual disability, severe
MedGen UID:
48638
Concept ID:
C0036857
Mental or Behavioral Dysfunction
Severe mental retardation is defined as an intelligence quotient (IQ) in the range of 20-34.
Encephalopathy
MedGen UID:
39314
Concept ID:
C0085584
Disease or Syndrome
Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state.
Polyneuropathy
MedGen UID:
57502
Concept ID:
C0152025
Disease or Syndrome
A generalized disorder of peripheral nerves.
Unsteady gait
MedGen UID:
68544
Concept ID:
C0231686
Finding
A shaky or wobbly manner of walking.
Memory impairment
MedGen UID:
68579
Concept ID:
C0233794
Mental or Behavioral Dysfunction
An impairment of memory as manifested by a reduced ability to remember things such as dates and names, and increased forgetfulness.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Positive Romberg sign
MedGen UID:
66017
Concept ID:
C0240914
Finding
The patient stands with the feet placed together and balance and is asked to close his or her eyes. A loss of balance upon eye closure is a positive Romberg sign and is interpreted as indicating a deficit in proprioception.
Parkinsonian disorder
MedGen UID:
66079
Concept ID:
C0242422
Disease or Syndrome
Characteristic neurologic anomaly resulting from degeneration of dopamine-generating cells in the substantia nigra, a region of the midbrain, characterized clinically by shaking, rigidity, slowness of movement and difficulty with walking and gait.
Motor polyneuropathy
MedGen UID:
82885
Concept ID:
C0271683
Disease or Syndrome
Inflammation or degeneration of the peripheral motor nerves.
Pain insensitivity
MedGen UID:
488855
Concept ID:
C0344307
Finding
Inability to perceive painful stimuli.
Steppage gait
MedGen UID:
98105
Concept ID:
C0427149
Finding
An abnormal gait pattern that arises from weakness of the pretibial and peroneal muscles due to a lower motor neuron lesion. Affected patients have footdrop and are unable to dorsiflex and evert the foot. The leg is lifted high on walking so that the toes clear the ground, and there may be a slapping noise when the foot strikes the ground again.
Incoordination
MedGen UID:
141714
Concept ID:
C0520966
Finding
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.
Gait disturbance
MedGen UID:
107895
Concept ID:
C0575081
Finding
The term gait disturbance can refer to any disruption of the ability to walk.
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
Increased CSF lactate
MedGen UID:
257904
Concept ID:
C1167918
Finding
Increased concentration of lactate in the cerebrospinal fluid.
Peripheral axonal neuropathy
MedGen UID:
266071
Concept ID:
C1263857
Disease or Syndrome
An abnormality characterized by disruption of the normal functioning of peripheral axons.
Impaired vibratory sensation
MedGen UID:
220959
Concept ID:
C1295585
Finding
A decrease in the ability to perceive vibration. Clinically, this is usually tested with a tuning fork which vibrates at 128 Hz and is applied to bony prominences such as the malleoli at the ankles or the metacarpal-phalangeal joints. There is a slow decay of vibration from the tuning fork. The degree of vibratory sense loss can be crudely estimated by counting the number of seconds that the examiner can perceive the vibration longer than the patient.
Increased CSF protein concentration
MedGen UID:
329971
Concept ID:
C1806780
Finding
Increased concentration of protein in the cerebrospinal fluid.
Gait imbalance
MedGen UID:
373028
Concept ID:
C1836150
Finding
Developmental regression
MedGen UID:
324613
Concept ID:
C1836830
Disease or Syndrome
Loss of developmental skills, as manifested by loss of developmental milestones.
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.
Delayed gross motor development
MedGen UID:
332508
Concept ID:
C1837658
Finding
A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.
Postural instability
MedGen UID:
334529
Concept ID:
C1843921
Finding
A tendency to fall or the inability to keep oneself from falling; imbalance. The retropulsion test is widely regarded as the gold standard to evaluate postural instability, Use of the retropulsion test includes a rapid balance perturbation in the backward direction, and the number of balance correcting steps (or total absence thereof) is used to rate the degree of postural instability. Healthy subjects correct such perturbations with either one or two large steps, or without taking any steps, hinging rapidly at the hips while swinging the arms forward as a counterweight. In patients with balance impairment, balance correcting steps are often too small, forcing patients to take more than two steps. Taking three or more steps is generally considered to be abnormal, and taking more than five steps is regarded as being clearly abnormal. Markedly affected patients continue to step backward without ever regaining their balance and must be caught by the examiner (this would be called true retropulsion). Even more severely affected patients fail to correct entirely, and fall backward like a pushed toy soldier, without taking any corrective steps.
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
Hyperintensity of cerebral white matter on MRI
MedGen UID:
811125
Concept ID:
C2938912
Pathologic Function
A brighter than expected signal on magnetic resonance imaging emanating from the cerebral white matter.
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.
Impaired distal tactile sensation
MedGen UID:
867225
Concept ID:
C4021583
Finding
A reduced sense of touch (tactile sensation) on the skin of the distal limbs. This is usually tested with a wisp of cotton or a fine camel's hair brush, by asking patients to say 'now' each time they feel the stimulus.
Impaired distal proprioception
MedGen UID:
867227
Concept ID:
C4021585
Finding
A loss or impairment of the sensation of the relative position of parts of the body and joint position occurring at distal joints.
Delayed CNS myelination
MedGen UID:
867393
Concept ID:
C4021758
Anatomical Abnormality
Delayed myelination in the central nervous system.
Elevated brain lactate level by MRS
MedGen UID:
868368
Concept ID:
C4022762
Finding
An increase in the level of lactate in the brain identified by magnetic resonance spectroscopy (MRS).
Impaired executive functioning
MedGen UID:
1617231
Concept ID:
C4544271
Mental or Behavioral Dysfunction
A disturbance of executive functioning, which is broadly defined as the set of abilities that allow for the planning, executing, monitoring, and self-correcting of goal-directed behavior while inhibiting task-irrelevant behavior. At least some degree of executive skill is needed to complete most cognitive tasks, and deficits in executive abilities are central to many clinical conditions, including fronto-temporal dementia.
Reduced cerebral white matter volume
MedGen UID:
1815057
Concept ID:
C5706151
Finding
An abnormally low volume of the white matter of the brain.
Abnormality of the coagulation cascade
MedGen UID:
604
Concept ID:
C0005779
Disease or Syndrome
An abnormality of the coagulation cascade, which is comprised of the contact activation pathway (also known as the intrinsic pathway) and the tissue factor pathway (also known as the extrinsic pathway) as well as cofactors and regulators.
Prolonged partial thromboplastin time
MedGen UID:
66815
Concept ID:
C0240671
Finding
Increased time to coagulation in the partial thromboplastin time (PTT) test, a measure of the intrinsic and common coagulation pathways. Phospholipid, and activator, and calcium are mixed into an anticoagulated plasma sample, and the time is measured until a thrombus forms.
Hypofibrinogenemia
MedGen UID:
107511
Concept ID:
C0553681
Disease or Syndrome
Decreased concentration of fibrinogen in the blood.
Prolonged prothrombin time
MedGen UID:
208879
Concept ID:
C0853225
Finding
Increased time to coagulation in the prothrombin time test, which is a measure of the extrinsic pathway of coagulation. The results of the prothrombin time test are often expressed in terms of the International normalized ratio (INR), which is calculated as a ratio of the patient's prothrombin time (PT) to a control PT standardized for the potency of the thromboplastin reagent developed by the World Health Organization (WHO) using the formula
Muscle flaccidity
MedGen UID:
10131
Concept ID:
C0026825
Sign or Symptom
A type of paralysis in which a muscle becomes soft and yields to passive stretching, which results from loss of all or practically all peripheral motor nerves that innervated the muscle. Muscle tone is reduced and the affected muscles undergo extreme atrophy within months of the loss of innervation.
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.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Muscle weakness
MedGen UID:
57735
Concept ID:
C0151786
Finding
Reduced strength of muscles.
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).
Generalized amyotrophy
MedGen UID:
234650
Concept ID:
C1389113
Disease or Syndrome
Generalized (diffuse, unlocalized) amyotrophy (muscle atrophy) affecting multiple muscles.
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.
Progressive proximal muscle weakness
MedGen UID:
322841
Concept ID:
C1836156
Finding
Lack of strength of the proximal muscles that becomes progressively more severe.
Distal lower limb amyotrophy
MedGen UID:
324515
Concept ID:
C1836451
Disease or Syndrome
Muscular atrophy of distal leg muscles.
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).
Intrinsic hand muscle atrophy
MedGen UID:
351202
Concept ID:
C1864716
Finding
Atrophy of the intrinsic muscle groups of the hand, comprising the thenar and hypothenar muscles; the interossei muscles; and the lumbrical muscles.
Ankle weakness
MedGen UID:
1624738
Concept ID:
C2228039
Finding
Reduced strength of the muscles that lift or otherwise move the foot at the ankle.
Ragged-red muscle fibers
MedGen UID:
477048
Concept ID:
C3275417
Finding
An abnormal appearance of muscle fibers observed on muscle biopsy. Ragged red fibers can be visualized with Gomori trichrome staining as irregular and intensely red subsarcolemmal zones, whereas the normal myofibrils are green. The margins of affect fibers appear red and ragged. The ragged-red is due to the accumulation of abnormal mitochondria below the plasma membrane of the muscle fiber, leading to the appearance of a red rim and speckled sarcoplasm.
EMG: myopathic abnormalities
MedGen UID:
867362
Concept ID:
C4021726
Pathologic Function
The presence of abnormal electromyographic patterns indicative of myopathy, such as small-short polyphasic motor unit potentials.
Appendicular hypotonia
MedGen UID:
868520
Concept ID:
C4022919
Finding
Muscular hypotonia of one or more limbs.
Microcephaly
MedGen UID:
1644158
Concept ID:
C4551563
Finding
Head circumference below 2 standard deviations below the mean for age and gender.
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.
Respiratory insufficiency due to muscle weakness
MedGen UID:
812797
Concept ID:
C3806467
Finding
Pancreatitis
MedGen UID:
14586
Concept ID:
C0030305
Disease or Syndrome
The presence of inflammation in the pancreas.
Splenomegaly
MedGen UID:
52469
Concept ID:
C0038002
Finding
Abnormal increased size of the spleen.
Antinuclear antibody positivity
MedGen UID:
101792
Concept ID:
C0151480
Laboratory or Test Result
The presence of autoantibodies in the serum that react against nuclei or nuclear components.
Osteomyelitis leading to amputation due to slow healing fractures
MedGen UID:
351263
Concept ID:
C1864975
Finding
Cytoplasmic antineutrophil antibody positivity
MedGen UID:
1690999
Concept ID:
C5139210
Finding
The presence of autoantibodies in the serum that react against proteins predominantly expressed in cytoplasmic granules of neutrophils.
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.
Dehydration
MedGen UID:
8273
Concept ID:
C0011175
Disease or Syndrome
A condition resulting from the excessive loss of water from the body. It is usually caused by severe diarrhea, vomiting or diaphoresis.
Type 2 diabetes mellitus
MedGen UID:
41523
Concept ID:
C0011860
Disease or Syndrome
WFS1 spectrum disorder (WFS1-SD) comprises classic WFS1 spectrum disorder and nonclassic WFS1 spectrum disorder. Classic WFS1-SD, a progressive neurodegenerative disorder, is characterized by onset of diabetes mellitus and optic atrophy before age 16 years. Additional complications may include one or more of the following: variable hearing impairment / deafness, diabetes insipidus, neurologic abnormalities, neurogenic bladder, and psychiatric abnormalities. Nonclassic WFS1-SD is less common than classic WFS1-SD. Phenotypes that appear to be milder than classic WFS1-SD include: optic atrophy and hearing impairment; neonatal diabetes, profound congenital deafness, and cataracts; isolated diabetes mellitus; isolated congenital cataracts; and isolated congenital, slowly progressive, and low-frequency (<2000 Hz) sensorineural hearing loss.
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.
Elevated circulating alpha-fetoprotein concentration
MedGen UID:
65916
Concept ID:
C0235971
Finding
Concentration of alpha-fetoprotein in the blood circulation above the upper limit of normal.
Hypoalbuminemia
MedGen UID:
68694
Concept ID:
C0239981
Finding
Reduction in the concentration of albumin in the blood.
Increased circulating ferritin concentration
MedGen UID:
69130
Concept ID:
C0241013
Finding
Increased concentration of ferritin in the blood circulation.
Conjugated hyperbilirubinemia
MedGen UID:
82787
Concept ID:
C0268307
Disease or Syndrome
Abnormally high level of conjugated bilirubin in the blood.
Hyperbilirubinemia
MedGen UID:
86321
Concept ID:
C0311468
Finding
An increased amount of bilirubin in the blood.
Elevated circulating alkaline phosphatase concentration
MedGen UID:
727252
Concept ID:
C1314665
Finding
Abnormally increased serum levels of alkaline phosphatase activity.
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).
Recurrent hypoglycemia
MedGen UID:
335382
Concept ID:
C1846288
Finding
Recurrent episodes of decreased concentration of glucose in the blood.
Increased circulating pyruvate concentration
MedGen UID:
376596
Concept ID:
C1849488
Finding
The concentration of pyruvate in the blood circulation is above the upper limit of normal.
Hypertyrosinemia
MedGen UID:
742296
Concept ID:
C1879362
Disease or Syndrome
An increased concentration of tyrosine in the blood.
Increased serum bile acid concentration
MedGen UID:
868605
Concept ID:
C4023004
Finding
An increase in the concentration of bile acid 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.
Elevated lactate:pyruvate ratio
MedGen UID:
1717835
Concept ID:
C5397670
Finding
An abnormal increase in the molar ratio of lactate to pyruvate in the blood circulation.
Hyperammonemia
MedGen UID:
1802066
Concept ID:
C5574662
Laboratory or Test Result
An increased concentration of ammonia in the blood.
Weak cry
MedGen UID:
65892
Concept ID:
C0234860
Finding
Wide nasal bridge
MedGen UID:
341441
Concept ID:
C1849367
Finding
Increased breadth of the nasal bridge (and with it, the nasal root).
Scaling skin
MedGen UID:
472970
Concept ID:
C0237849
Finding
Refers to the loss of the outer layer of the epidermis in large, scale-like flakes.
Brittle hair
MedGen UID:
120480
Concept ID:
C0263490
Disease or Syndrome
Fragile, easily breakable hair, i.e., with reduced tensile strength.
Reticular hyperpigmentation
MedGen UID:
338832
Concept ID:
C1851972
Finding
Increased pigmentation of the skin with a netlike (reticular) pattern.
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.
Hypoparathyroidism
MedGen UID:
6985
Concept ID:
C0020626
Disease or Syndrome
A condition caused by a deficiency of parathyroid hormone characterized by hypocalcemia and hyperphosphatemia.
Hypothyroidism
MedGen UID:
6991
Concept ID:
C0020676
Disease or Syndrome
Deficiency of thyroid hormone.
Reduced circulating growth hormone concentration
MedGen UID:
82880
Concept ID:
C0271561
Disease or Syndrome
Concentration of growth hormone in the blood circulation below normal limits.
Decreased circulating cortisol level
MedGen UID:
322961
Concept ID:
C1836623
Finding
Abnormally reduced concentration of cortisol in the blood.
Ptosis
MedGen UID:
2287
Concept ID:
C0005745
Disease or Syndrome
The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective).
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.
Horizontal nystagmus
MedGen UID:
124399
Concept ID:
C0271385
Disease or Syndrome
Nystagmus consisting of horizontal to-and-fro eye movements.
Ophthalmoparesis
MedGen UID:
155551
Concept ID:
C0751401
Sign or Symptom
Ophthalmoplegia is a paralysis or weakness of one or more of the muscles that control eye movement.
Retinal dystrophy
MedGen UID:
208903
Concept ID:
C0854723
Finding
Retinal dystrophy is an abnormality of the retina associated with a hereditary process. Retinal dystrophies are defined by their predominantly monogenic inheritance and they are frequently associated with loss or dysfunction of photoreceptor cells as a primary or secondary event.
Pigmentary retinopathy
MedGen UID:
1643295
Concept ID:
C4551715
Disease or Syndrome
An abnormality of the retina characterized by pigment deposition. It is typically associated with migration and proliferation of macrophages or retinal pigment epithelial cells into the retina; melanin from these cells causes the pigmentary changes. Pigmentary retinopathy is a common final pathway of many retinal conditions and is often associated with visual loss.
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.
Multiple mitochondrial DNA deletions
MedGen UID:
479006
Concept ID:
C3277376
Finding
The presence of multiple deletions of mitochondrial DNA (mtDNA).
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.
Depletion of mitochondrial DNA in muscle tissue
MedGen UID:
867163
Concept ID:
C4021521
Finding
Mitochondrial depletion
MedGen UID:
868267
Concept ID:
C4022659
Finding
An abnormal reduction in mitochondrial DNA content of cells.

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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