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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; CMT 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.

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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