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Giant axonal neuropathy 1(GAN1)

MedGen UID:
376775
Concept ID:
C1850386
Disease or Syndrome
Synonyms: GAN1; GIANT AXONAL NEUROPATHY 1, AUTOSOMAL RECESSIVE
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): GAN (16q23.2)
 
Monarch Initiative: MONDO:0009749
OMIM®: 256850
Orphanet: ORPHA643

Disease characteristics

Excerpted from the GeneReview: GAN-Related Neurodegeneration
GAN-related neurodegeneration comprises a phenotypic continuum ranging from severe (sometimes called classic giant axonal neuropathy) to milder pure early-onset peripheral motor and sensory neuropathies. The classic giant axonal neuropathy phenotype typically manifests as an infantile-onset neurodegenerative disorder, starting as a severe peripheral motor and sensory neuropathy and evolving into central nervous system impairment (intellectual disability, seizures, cerebellar signs, and pyramidal tract signs). Most affected individuals become wheelchair dependent in the second decade of life and eventually bedridden with severe polyneuropathy, ataxia, and dementia. Death usually occurs in the third decade. At the milder end of the spectrum are predominantly motor and sensory neuropathies (with little to no CNS involvement) that overlap with the axonal form of Charcot-Marie-Tooth neuropathies. [from GeneReviews]
Authors:
Puneet Opal   view full author information

Additional descriptions

From OMIM
Giant axonal neuropathy is a chronic polyneuropathy of childhood that affects both the peripheral and central nervous systems and is accompanied by characteristically kinky hair and unique posture of legs (see illustrations by Berg et al., 1972; Igisu et al., 1975; Carpenter et al., 1974). Axonal loss and the presence of giant axonal swellings filled with neurofilaments on nerve biopsy are the pathologic hallmark of this neurodegenerative disorder (Tazir et al., 2009). Genetic Heterogeneity of Giant Axonal Neuropathy See also GAN2 (610100), caused by mutation in the DCAF8 gene (615820) on chromosome 1q23.  http://www.omim.org/entry/256850
From MedlinePlus Genetics
Giant axonal neuropathy is an inherited condition characterized by abnormally large and dysfunctional axons called giant axons. Axons are specialized extensions of nerve cells (neurons) that transmit nerve impulses. Symptoms of the disorder first become apparent in the peripheral nervous system, in which long axons connect the brain and spinal cord (central nervous system) to muscles and to sensory cells that detect sensations such as touch, pain, heat, and sound. However, axons in the central nervous system are affected as well.

The signs and symptoms of giant axonal neuropathy generally begin in early childhood and get worse over time. Most affected individuals first have problems with walking. Later they may lose sensation, strength, and reflexes in their limbs; experience difficulty coordinating movements (ataxia); and require wheelchair assistance. Many affected individuals have an abnormal curvature of the spine (scoliosis). Visual and hearing problems may also occur. Many individuals with this condition have extremely kinky hair as compared to others in their family.

Giant axonal neuropathy can also impact the autonomic nervous system, which controls involuntary body processes. Affected individuals may experience problems with constipation, heat intolerance, and the release of urine (neurogenic bladder), and a reduction in or loss of the ability to sweat.

As the disorder worsens, paralysis, seizures, difficulty breathing or swallowing, and a gradual decline in mental function (dementia) can also occur. Most people with giant axonal neuropathy do not survive past their twenties.

Some affected individuals have a milder form of giant axonal neuropathy that begins later in life. Movement problems in these individuals are less severe, and the signs and symptoms usually worsen at a slower rate than in the classic form of the condition. Individuals with the milder form often have straight hair, and they may survive into adulthood.  https://medlineplus.gov/genetics/condition/giant-axonal-neuropathy

Clinical features

From HPO
Clubfoot
MedGen UID:
3130
Concept ID:
C0009081
Congenital Abnormality
Clubfoot is a congenital limb deformity defined as fixation of the foot in cavus, adductus, varus, and equinus (i.e., inclined inwards, axially rotated outwards, and pointing downwards) with concomitant soft tissue abnormalities (Cardy et al., 2007). Clubfoot may occur in isolation or as part of a syndrome (e.g., diastrophic dysplasia, 222600). Clubfoot has been reported with deficiency of long bones and mirror-image polydactyly (Gurnett et al., 2008; Klopocki et al., 2012).
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.
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).
Hyporeflexia of lower limbs
MedGen UID:
371881
Concept ID:
C1834696
Finding
Reduced intensity of muscle tendon reflexes in the lower limbs. Reflexes are elicited by stretching the tendon of a muscle, e.g., by tapping.
Areflexia of lower limbs
MedGen UID:
347285
Concept ID:
C1856694
Finding
Inability to elicit tendon reflexes in the lower limbs.
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.
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.
Spastic paraplegia
MedGen UID:
20882
Concept ID:
C0037772
Disease or Syndrome
Spasticity and weakness of the leg and hip muscles.
Photophobia
MedGen UID:
43220
Concept ID:
C0085636
Sign or Symptom
Excessive sensitivity to light with the sensation of discomfort or pain in the eyes due to exposure to bright light.
Hyperreflexia
MedGen UID:
57738
Concept ID:
C0151889
Finding
Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.
Abnormal pyramidal sign
MedGen UID:
68582
Concept ID:
C0234132
Sign or Symptom
Functional neurological abnormalities related to dysfunction of the pyramidal tract.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
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.
Sensory axonal neuropathy
MedGen UID:
334116
Concept ID:
C1842587
Finding
An axonal neuropathy of peripheral sensory nerves.
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.
Lateral ventricle dilatation
MedGen UID:
383904
Concept ID:
C1856409
Pathologic Function
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).
Abnormal cerebellum morphology
MedGen UID:
400925
Concept ID:
C1866129
Anatomical Abnormality
Any structural abnormality of the cerebellum.
Motor axonal neuropathy
MedGen UID:
413108
Concept ID:
C2749625
Disease or Syndrome
Progressive impairment of function of motor axons with muscle weakness, atrophy, and cramps. The deficits are length-dependent, meaning that muscles innervated by the longest nerves are affected first, so that for instance the arms are affected at a later age than the onset of deficits involving the lower leg.
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.
Abnormal pyramidal tract morphology
MedGen UID:
892809
Concept ID:
C4021761
Anatomical Abnormality
Any structural abnormality of the pyramidal tract, whose chief element, the corticospinal tract, is the only direct connection between the brain and the spinal cord. In addition to the corticospinal tract, the pyramidal system includes the corticobulbar, corticomesencephalic, and corticopontine tracts.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Proximal muscle weakness
MedGen UID:
113169
Concept ID:
C0221629
Finding
A lack of strength of the proximal muscles.
Facial palsy
MedGen UID:
87660
Concept ID:
C0376175
Disease or Syndrome
Facial nerve palsy is a dysfunction of cranial nerve VII (the facial nerve) that results in inability to control facial muscles on the affected side with weakness of the muscles of facial expression and eye closure. This can either be present in unilateral or bilateral form.
Distal muscle weakness
MedGen UID:
140883
Concept ID:
C0427065
Finding
Reduced strength of the musculature of the distal extremities.
Distal amyotrophy
MedGen UID:
338530
Concept ID:
C1848736
Disease or Syndrome
Muscular atrophy affecting muscles in the distal portions of the extremities.
Macrocephaly
MedGen UID:
745757
Concept ID:
C2243051
Finding
Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium.
Curly hair
MedGen UID:
488919
Concept ID:
C0558165
Finding
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.
Strabismus
MedGen UID:
21337
Concept ID:
C0038379
Disease or Syndrome
A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
Follow this link to review classifications for Giant axonal neuropathy 1 in Orphanet.

Professional guidelines

PubMed

Chakravorty S, Logan R, Elson MJ, Luke RR, Verma S
Sci Rep 2020 Sep 30;10(1):16184. doi: 10.1038/s41598-020-73219-5. PMID: 32999401Free PMC Article
Chen PH, Hu J, Wu J, Huynh DT, Smith TJ, Pan S, Bisnett BJ, Smith AB, Lu A, Condon BM, Chi JT, Boyce M
JCI Insight 2020 Jan 16;5(1) Epub 2019 Nov 26 doi: 10.1172/jci.insight.127751. PMID: 31944090Free PMC Article
Koop O, Schirmacher A, Nelis E, Timmerman V, De Jonghe P, Ringelstein B, Rasic VM, Evrard P, Gärtner J, Claeys KG, Appenzeller S, Rautenstrauss B, Hühne K, Ramos-Arroyo MA, Wörle H, Moilanen JS, Hammans S, Kuhlenbäumer G
Neuromuscul Disord 2007 Aug;17(8):624-30. Epub 2007 Jun 22 doi: 10.1016/j.nmd.2007.03.012. PMID: 17587580

Curated

Aretz S, Rautenstrauss B, Timmerman V
Eur J Hum Genet 2010 Sep;18(9) Epub 2010 May 26 doi: 10.1038/ejhg.2010.75. PMID: 20512157Free PMC Article

Recent clinical studies

Therapy

Tazir M, Vallat JM, Bomont P, Zemmouri R, Sindou P, Assami S, Nouioua S, Hammadouche T, Grid D, Koenig M
Neuromuscul Disord 2002 Nov;12(9):849-52. doi: 10.1016/s0960-8966(02)00029-9. PMID: 12398836

Prognosis

Tazir M, Vallat JM, Bomont P, Zemmouri R, Sindou P, Assami S, Nouioua S, Hammadouche T, Grid D, Koenig M
Neuromuscul Disord 2002 Nov;12(9):849-52. doi: 10.1016/s0960-8966(02)00029-9. PMID: 12398836

Supplemental Content

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    Clinical resources

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    • PubMed
      See practice and clinical guidelines in PubMed. The search results may include broader topics and may not capture all published guidelines. See the FAQ for details.

    Curated

    • EuroGenetest, 2010
      Clinical utility gene card for: HMSN/HNPP HMSN types 1, 2, 3, 6 (CMT1,2,4, DSN, CHN, GAN, CCFDN, HNA); HNPP

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