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Charcot-Marie-Tooth disease type 2A2(CMT2A2A)

MedGen UID:
1648317
Concept ID:
C4721887
Disease or Syndrome
Synonyms: CHARCOT-MARIE-TOOTH DISEASE, AXONAL, AUTOSOMAL DOMINANT, TYPE 2A2A; CHARCOT-MARIE-TOOTH DISEASE, AXONAL, TYPE 2A2; CHARCOT-MARIE-TOOTH DISEASE, NEURONAL, TYPE 2A2; Charcot-Marie-Tooth disease, type 2A2A; Charcot-Marie-Tooth Neuropathy Type 2A2; HEREDITARY MOTOR AND SENSORY NEUROPATHY IIA2; HMSN IIA2
SNOMED CT: Autosomal dominant Charcot-Marie-Tooth disease type 2A2 (764850002)
Modes of inheritance:
Autosomal dominant inheritance
MedGen UID:
141047
Concept ID:
C0443147
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 heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele.
 
Gene (location): MFN2 (1p36.22)
 
Monarch Initiative: MONDO:0012231
OMIM®: 609260
Orphanet: ORPHA99947

Definition

MFN2 hereditary motor and sensory neuropathy (MFN2-HMSN) is a classic axonal peripheral sensorimotor neuropathy, inherited in either an autosomal dominant (AD) manner (~90%) or an autosomal recessive (AR) manner (~10%). MFN2-HMSN is characterized by more severe involvement of the lower extremities than the upper extremities, distal upper-extremity involvement as the neuropathy progresses, more prominent motor deficits than sensory deficits, and normal (>42 m/s) or only slightly decreased nerve conduction velocities (NCVs). Postural tremor is common. Median onset is age 12 years in the AD form and age eight years in the AR form. The prevalence of optic atrophy is approximately 7% in the AD form and approximately 20% in the AR form. [from GeneReviews]

Additional description

From OMIM
Charcot-Marie-Tooth disease constitutes a clinically and genetically heterogeneous group of hereditary motor and sensory neuropathies. On the basis of electrophysiologic criteria, CMT is divided into 2 major types: type 1, the demyelinating form, characterized by a slow motor median nerve conduction velocity (NCV) (less than 38 m/s), and type 2, the axonal form, with a normal or slightly reduced NCV. Distal hereditary motor neuropathy (dHMN), also known as spinal CMT, is a third type of CMT characterized by normal motor and sensory NCV and degeneration of spinal cord anterior horn cells. See CMT1B (118200) and CMT1A (118220) for descriptions of autosomal dominant slow nerve conduction types of Charcot-Marie-Tooth disease. See CMT4A (214400) and CMTX1 (302800) for autosomal recessive and X-linked forms of Charcot-Marie-Tooth disease, respectively. For a discussion of genetic heterogeneity of axonal CMT type 2, see 118210.  http://www.omim.org/entry/609260

Clinical features

From HPO
Pain
MedGen UID:
45282
Concept ID:
C0030193
Sign or Symptom
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Limb muscle weakness
MedGen UID:
107956
Concept ID:
C0587246
Finding
Reduced strength and weakness of the muscles of the arms and legs.
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.
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.
Hearing impairment
MedGen UID:
235586
Concept ID:
C1384666
Disease or Syndrome
A decreased magnitude of the sensory perception of sound.
Spasticity
MedGen UID:
7753
Concept ID:
C0026838
Sign or Symptom
A motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes with increased muscle tone, exaggerated (hyperexcitable) tendon reflexes.
Babinski sign
MedGen UID:
19708
Concept ID:
C0034935
Finding
Upturning of the big toe (and sometimes fanning of the other toes) in response to stimulation of the sole of the foot. If the Babinski sign is present it can indicate damage to the corticospinal tract.
Tremor
MedGen UID:
21635
Concept ID:
C0040822
Sign or Symptom
An unintentional, oscillating to-and-fro muscle movement about a joint axis.
Hyperreflexia
MedGen UID:
57738
Concept ID:
C0151889
Finding
Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Mental deterioration
MedGen UID:
66713
Concept ID:
C0234985
Mental or Behavioral Dysfunction
Loss of previously present mental abilities, generally in adults.
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.
Hyporeflexia
MedGen UID:
195967
Concept ID:
C0700078
Finding
Reduction of neurologic reflexes such as the knee-jerk reaction.
Distal sensory impairment
MedGen UID:
335722
Concept ID:
C1847584
Finding
An abnormal reduction in sensation in the distal portions of the extremities.
Onion bulb formation
MedGen UID:
376237
Concept ID:
C1847906
Finding
Repeated episodes of segmental demyelination and remyelination lead to the accumulation of supernumerary Schwann cells around axons, which is referred to as onion bulb formation. This finding affects peripheral nerves.
Decreased sensory nerve conduction velocity
MedGen UID:
336512
Concept ID:
C1849148
Finding
Reduced speed of conduction of the action potential along a sensory nerve.
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).
Decreased motor nerve conduction velocity
MedGen UID:
388130
Concept ID:
C1858729
Finding
A type of decreased nerve conduction velocity that affects the motor neuron.
Axonal degeneration/regeneration
MedGen UID:
368889
Concept ID:
C1968790
Finding
A pattern of simultaneous degeneration and regeneration of axons (see comment).
Peripheral axonal atrophy
MedGen UID:
871146
Concept ID:
C4025619
Disease or Syndrome
Atrophic changes of axons of the peripheral nervous system.
Hypertonia
MedGen UID:
10132
Concept ID:
C0026826
Finding
A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Flexion contracture
MedGen UID:
83069
Concept ID:
C0333068
Anatomical Abnormality
A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints.
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.
Optic atrophy
MedGen UID:
18180
Concept ID:
C0029124
Disease or Syndrome
Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

Professional guidelines

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

Etiology

Xu X, Lu F, Du S, Zhang L
BMC Pediatr 2024 Jan 5;24(1):21. doi: 10.1186/s12887-023-04441-z. PMID: 38183043Free PMC Article

Diagnosis

Xu X, Lu F, Du S, Zhang L
BMC Pediatr 2024 Jan 5;24(1):21. doi: 10.1186/s12887-023-04441-z. PMID: 38183043Free PMC Article

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