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Charcot-Marie-Tooth disease type 2B1(CMT2B1)

MedGen UID:
343064
•Concept ID:
C1854154
•
Disease or Syndrome
Synonyms: Charcot-marie-tooth disease, axonal, type 2b1; CHARCOT-MARIE-TOOTH DISEASE, NEURONAL, TYPE 2B1; Charcot-Marie-Tooth Neuropathy Type 2B1; CMT2B1
SNOMED CT: Charcot-Marie-Tooth disease type 2B1 (725048002); Autosomal recessive Charcot-Marie-Tooth disease type 2B1 (725048002)
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): LMNA (1q22)
 
Monarch Initiative: MONDO:0011569
OMIM®: 605588
Orphanet: ORPHA98856

Definition

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 motor median nerve conduction velocity less than 38 m/s (see CMT1B; 118200); and type 2, the axonal form, with a normal or slightly reduced nerve conduction velocity. For a phenotypic description and a discussion of genetic heterogeneity of axonal CMT type 2, see CMT2A1 (118210). [from OMIM]

Clinical features

From HPO
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).
Upper limb muscle weakness
MedGen UID:
305607
•Concept ID:
C1698196
•
Finding
Weakness of the muscles of the arms.
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.
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.
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 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.
Proximal muscle weakness
MedGen UID:
113169
•Concept ID:
C0221629
•
Finding
A lack of strength of the proximal muscles.
Distal muscle weakness
MedGen UID:
140883
•Concept ID:
C0427065
•
Finding
Reduced strength of the musculature of the distal extremities.
Kyphoscoliosis
MedGen UID:
154361
•Concept ID:
C0575158
•
Anatomical Abnormality
An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.
Distal amyotrophy
MedGen UID:
338530
•Concept ID:
C1848736
•
Disease or Syndrome
Muscular atrophy affecting muscles in the distal portions of the extremities.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
  • CROGVCharcot-Marie-Tooth disease type 2B1
Follow this link to review classifications for Charcot-Marie-Tooth disease type 2B1 in Orphanet.

Professional guidelines

Recent clinical studies

Etiology

Liang JJ, Grogan M, Ackerman MJ, Goodsell K
J Cardiovasc Electrophysiol 2016 Jul;27(7):868-71. Epub 2016 May 31 doi: 10.1111/jce.12984. PMID: 27405450

Diagnosis

Liang JJ, Grogan M, Ackerman MJ, Goodsell K
J Cardiovasc Electrophysiol 2016 Jul;27(7):868-71. Epub 2016 May 31 doi: 10.1111/jce.12984. PMID: 27405450

Prognosis

Liang JJ, Grogan M, Ackerman MJ, Goodsell K
J Cardiovasc Electrophysiol 2016 Jul;27(7):868-71. Epub 2016 May 31 doi: 10.1111/jce.12984. PMID: 27405450

Clinical prediction guides

Liang JJ, Grogan M, Ackerman MJ, Goodsell K
J Cardiovasc Electrophysiol 2016 Jul;27(7):868-71. Epub 2016 May 31 doi: 10.1111/jce.12984. PMID: 27405450

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