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Neuronopathy, distal hereditary motor, type 2A(HMN2A; DHMN2A; HMND2)

MedGen UID:: 322471
•Concept ID:: C1834692
•: Disease or Syndrome

Synonyms:	CHARCOT-MARIE-TOOTH DISEASE, SPINAL, IIA; Distal Hereditary Motor Neuronopathy, Type IIA; HMN IIA; NEURONOPATHY, DISTAL HEREDITARY MOTOR, AUTOSOMAL DOMINANT 2; NEURONOPATHY, DISTAL HEREDITARY MOTOR, HARDING TYPE IIA; NEUROPATHY, DISTAL HEREDITARY MOTOR, HARDING TYPE IIA; SPINAL MUSCULAR ATROPHY, DISTAL, ADULT, AUTOSOMAL DOMINANT, HARDING TYPE IIA

Gene (location): Gene(s) directly associated with this condition or phenotype.	HSPB8 (12q24.23)

Monarch Initiative:	MONDO:0008025
OMIM®:	158590

Definition

Autosomal dominant distal hereditary motor neuronopathy-2 (HMND2) is a motor neuron disease without sensory loss with an onset age of 15 to 25 years. The presenting symptoms are paresis of the extensor muscles of the big toe and later of the extensor muscles of the feet. The disease progresses to complete paralysis of all distal muscles of the lower extremities. Affected individuals have chronic neurogenic alterations in electromyography (summary by Irobi et al., 2004). Some individuals show changes consistent with myofibrillar myopathy on muscle biopsy (Ghaoui et al., 2016). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal dominant distal HMN, see HMND1 (182960). [from OMIM]

Additional description

From MedlinePlus Genetics
Distal hereditary motor neuropathy, type II is a progressive disorder that affects nerve cells in the spinal cord. It results in muscle weakness and affects movement, primarily in the legs.

Onset of distal hereditary motor neuropathy, type II ranges from the teenage years through mid-adulthood. The initial symptoms of the disorder are cramps or weakness in the muscles of the big toe and later, the entire foot. Over a period of approximately 5 to 10 years, affected individuals experience a gradual loss of muscle tissue (atrophy) in the lower legs. They begin to have trouble walking and running, and eventually may have complete paralysis of the lower legs. The thigh muscles may also be affected, although generally this occurs later and is less severe.

Some individuals with distal hereditary motor neuropathy, type II have weakening of the muscles in the hands and forearms. This weakening is less pronounced than in the lower limbs and does not usually result in paralysis. https://medlineplus.gov/genetics/condition/distal-hereditary-motor-neuropathy-type-ii

Clinical features

From HPO

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.

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Distal lower limb muscle weakness

MedGen UID:: 324514
•Concept ID:: C1836450
•: Finding

Reduced strength of the distal musculature of the legs.

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Areflexia of lower limbs

MedGen UID:: 347285
•Concept ID:: C1856694
•: Finding

Inability to elicit tendon reflexes in the lower limbs.

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Paralysis

MedGen UID:: 105510
•Concept ID:: C0522224
•: Finding

Paralysis of voluntary muscles means loss of contraction due to interruption of one or more motor pathways from the brain to the muscle fibers. Although the word paralysis is often used interchangeably to mean either complete or partial loss of muscle strength, it is preferable to use paralysis or plegia for complete or severe loss of muscle strength, and paresis for partial or slight loss. Motor paralysis results from deficits of the upper motor neurons (corticospinal, corticobulbar, or subcorticospinal). Motor paralysis is often accompanied by an impairment in the facility of movement.

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Distal muscle weakness

MedGen UID:: 140883
•Concept ID:: C0427065
•: Finding

Reduced strength of the musculature of the distal extremities.

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EMG: neuropathic changes

MedGen UID:: 867363
•Concept ID:: C4021727
•: Finding

The presence of characteristic findings of denervation on electromyography (fibrillations, positive sharp waves, and giant motor unit potentials).

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Paresis of extensor muscles of the big toe

MedGen UID:: 871217
•Concept ID:: C4025696
•: Finding

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Abnormality of limbs
Abnormality of the musculoskeletal system
Abnormality of the nervous system
- Paralysis

Term Hierarchy

GTR
MeSH

CClinical test, RResearch test, OOMIM, GGeneReviews, VClinVar

Distal spinal muscular atrophy
- Neuronopathy, distal hereditary motor, type 2A

Recent clinical studies

Diagnosis

Charcot-Marie-Tooth disease type 2C: a distinct genetic entity. Clinical and molecular characterization of the first European family.

Santoro L, Manganelli F, Di Maio L, Barbieri F, Carella M, D'Adamo P, Casari G
Neuromuscul Disord 2002 May;12(4):399-404. doi: 10.1016/s0960-8966(01)00305-4. PMID: 12062259

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Neuronopathy, distal hereditary motor, type 2A(HMN2A; DHMN2A; HMND2)

Definition

Additional description

Clinical features

Term Hierarchy

Recent clinical studies

Diagnosis

Supplemental Content

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Genetic Testing Registry

Clinical resources

Molecular resources

Consumer resources

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