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Charcot-Marie-Tooth disease, type 4B2(CMT4B2)

MedGen UID:
346869
Concept ID:
C1858278
Disease or Syndrome
Synonyms: CHARCOT-MARIE-TOOTH DISEASE, WITH FOCALLY FOLDED MYELIN SHEATHS, AUTOSOMAL RECESSIVE, TYPE 4B2; Charcot-Marie-Tooth Neuropathy Type 4B2; Charcot-Marie-Tooth Neuropathy Type 4B2 (CMT4B2); CMT 4B2; CMT4B2
Modes of inheritance:
Heterogeneous
MedGen UID:
67020
Concept ID:
C0242960
Organism Attribute
Source: HPO
The presence of apparently similar characters for which the genetic evidence indicates that different genes or different genetic mechanisms are involved in different pedigrees. In clinical settings genetic heterogeneity refers to the presence of a variety of genetic defects which cause the same disease, often due to mutations at different loci on the same gene, a finding common to many human diseases including ALZHEIMER DISEASE; CYSTIC FIBROSIS; LIPOPROTEIN LIPASE DEFICIENCY, FAMILIAL; and POLYCYSTIC KIDNEY DISEASES. (Rieger, et al., Glossary of Genetics: Classical and Molecular, 5th ed; Segen, Dictionary of Modern Medicine, 1992)
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Sources: HPO, OMIM, 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 homozygotes. In the context of medical genetics, autosomal recessive disorders manifest in homozygotes (with two copies of the mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
Autosomal recessive inheritance (HPO, OMIM, Orphanet)
SNOMED CT: Charcot-Marie-Tooth disease type 4B2 (715800000)
 
Gene (location): SBF2 (11p15.4)
OMIM®: 604563
Orphanet: ORPHA99956

Disease characteristics

Excerpted from the GeneReview: Charcot-Marie-Tooth Neuropathy Type 4
Charcot-Marie-Tooth neuropathy type 4 (CMT4) is a group of progressive motor and sensory axonal and demyelinating neuropathies that are distinguished from other forms of CMT by autosomal recessive inheritance. Affected individuals have the typical CMT phenotype of distal muscle weakness and atrophy associated with sensory loss and, frequently, pes cavus foot deformity. [from GeneReviews]
Authors:
Thomas D Bird   view full author information

Additional descriptions

From OMIM
Autosomal recessive Charcot-Marie-Tooth disease type 4B is a demyelinating hereditary motor and sensory neuropathy characterized by abnormal folding of myelin sheaths. CMT4B1 (601382) is a clinically similar disorder caused by mutation in the MTMR2 gene (603557) on 11q22. For a phenotypic description and a discussion of genetic heterogeneity of autosomal recessive demyelinating CMT, see CMT4A (214400).  http://www.omim.org/entry/604563
From GHR
Charcot-Marie-Tooth disease is a group of progressive disorders that affect the peripheral nerves. Peripheral nerves connect the brain and spinal cord to muscles and to sensory cells that detect sensations such as touch, pain, heat, and sound. Damage to the peripheral nerves can result in loss of sensation and wasting (atrophy) of muscles in the feet, legs, and hands.Charcot-Marie-Tooth disease usually becomes apparent in adolescence or early adulthood, but onset may occur anytime from early childhood through late adulthood. Symptoms of Charcot-Marie-Tooth disease vary in severity, even among members of the same family. Some people never realize they have the disorder, but most have a moderate amount of physical disability. A small percentage of people experience severe weakness or other problems which, in rare cases, can be life-threatening. In most affected individuals, however, Charcot-Marie-Tooth disease does not affect life expectancy.Typically, the earliest symptoms of Charcot-Marie-Tooth disease involve balance difficulties, clumsiness, and muscle weakness in the feet. Affected individuals may have foot abnormalities such as high arches (pes cavus), flat feet (pes planus), or curled toes (hammer toes). They often have difficulty flexing the foot or walking on the heel of the foot. These difficulties may cause a higher than normal step (or gait) and increase the risk of ankle injuries and tripping.As the disease progresses, muscles in the lower legs usually weaken, but leg and foot problems rarely require the use of a wheelchair. Affected individuals may also develop weakness in the hands, causing difficulty with daily activities such as writing, fastening buttons, and turning doorknobs. People with this disorder typically experience a decreased sensitivity to touch, heat, and cold in the feet and lower legs, but occasionally feel aching or burning sensations. In some cases, affected individuals experience gradual hearing loss, deafness, or loss of vision.There are several types of Charcot-Marie-Tooth disease. Type 1 Charcot-Marie-Tooth disease (CMT1) is characterized by abnormalities in myelin, the fatty substance that covers nerve cells, protecting them and helping to conduct nerve impulses. These abnormalities slow the transmission of nerve impulses. Type 2 Charcot-Marie-Tooth disease (CMT2) is characterized by abnormalities in the fiber, or axon, that extends from a nerve cell body and transmits nerve impulses. These abnormalities reduce the strength of the nerve impulse. Type 4 Charcot-Marie-Tooth disease (CMT4) affects either the axon or myelin and is distinguished from the other types by its pattern of inheritance. In intermediate forms of Charcot-Marie-Tooth disease, the nerve impulses are both slowed and reduced in strength, probably due to abnormalities in both axons and myelin. Type X Charcot-Marie-Tooth disease (CMTX) is caused by mutations in a gene on the X chromosome, one of the two sex chromosomes. Within the various types of Charcot-Marie-Tooth disease, subtypes (such as CMT1A, CMT1B, CMT2A, CMT4A, and CMTX1) are distinguished by the specific gene that is altered.Sometimes other, more historical names are used to describe this disorder. For example, Roussy-Levy syndrome is a form of Charcot-Marie-Tooth disease defined by the additional feature of rhythmic shaking (tremors). Dejerine-Sottas syndrome is a term sometimes used to describe a severe, early childhood form of Charcot-Marie-Tooth disease; it is also sometimes called Charcot-Marie-Tooth disease type 3 (CMT3). Depending on the specific gene that is altered, this severe, early onset form of the disorder may also be classified as CMT1 or CMT4. CMTX5 is also known as Rosenberg-Chutorian syndrome. Some researchers believe that this condition is not actually a form of Charcot-Marie-Tooth disease. Instead, they classify it as a separate disorder characterized by peripheral nerve problems, deafness, and vision loss.  https://ghr.nlm.nih.gov/condition/charcot-marie-tooth-disease

Clinical features

Glaucoma
MedGen UID:
42224
Concept ID:
C0017601
Disease or Syndrome
Glaucoma is a group of eye disorders in which the optic nerves connecting the eyes and the brain are progressively damaged. This damage can lead to reduction in side (peripheral) vision and eventual blindness. Other signs and symptoms may include bulging eyes, excessive tearing, and abnormal sensitivity to light (photophobia). The term "early-onset glaucoma" may be used when the disorder appears before the age of 40.In most people with glaucoma, the damage to the optic nerves is caused by increased pressure within the eyes (intraocular pressure). Intraocular pressure depends on a balance between fluid entering and leaving the eyes.Usually glaucoma develops in older adults, in whom the risk of developing the disorder may be affected by a variety of medical conditions including high blood pressure (hypertension) and diabetes mellitus, as well as family history. The risk of early-onset glaucoma depends mainly on heredity.Structural abnormalities that impede fluid drainage in the eye may be present at birth and usually become apparent during the first year of life. Such abnormalities may be part of a genetic disorder that affects many body systems, called a syndrome. If glaucoma appears before the age of 5 without other associated abnormalities, it is called primary congenital glaucoma.Other individuals experience early onset of primary open-angle glaucoma, the most common adult form of glaucoma. If primary open-angle glaucoma develops during childhood or early adulthood, it is called juvenile open-angle glaucoma.
Talipes equinovarus
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).
Foot-drop
MedGen UID:
88451
Concept ID:
C0085684
Disease or Syndrome
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.
Split hand
MedGen UID:
67457
Concept ID:
C0221373
Congenital Abnormality
A condition in which middle parts of the hand (fingers and metacarpals) are missing giving a cleft appearance. The severity is very variable ranging from slightly hypoplastic middle fingers over absent middel fingers as far as oligo- or monodactyl hands.
Pes cavus
MedGen UID:
675590
Concept ID:
C0728829
Congenital Abnormality
The presence of an unusually high plantar arch. Also called high instep, pes cavus refers to 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.
Ulnar claw
MedGen UID:
871311
Concept ID:
C4025799
Congenital Abnormality
An abnormal hand position characterized by hyperextension of the fourth and fifth fingers at the metacarpophalangeal joints and flexion of the interphalangeal joints of the same fingers such that they are curled towards the palm.
Sensorineural hearing loss
MedGen UID:
9164
Concept ID:
C0018784
Disease or Syndrome
Hearing loss resulting from damage to the COCHLEA and the sensorineural elements which lie internally beyond the oval and round windows. These elements include the AUDITORY NERVE and its connections in the BRAINSTEM.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Difficulty walking
MedGen UID:
86319
Concept ID:
C0311394
Finding
We walk thousands of steps each day. We walk to do our daily activities, get around, and exercise. Having a problem with walking can make daily life more difficult. . The pattern of how you walk is called your gait. A variety of problems can cause an abnormal gait and lead to problems with walking. These include: . -Injuries, diseases, or abnormal development of the muscles or bones of your legs or feet. -Movement disorders such as Parkinson's disease. -Diseases such as arthritis or multiple sclerosis. -Vision or balance problems. Treatment of walking problems depends on the cause. Physical therapy, surgery, or mobility aids may help.
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
Sign or Symptom
Reduction of neurologic reflexes such as the knee-jerk reaction.
Segmental peripheral demyelination/remyelination
MedGen UID:
335873
Concept ID:
C1843077
Finding
A segmental pattern of demyelination and regeneration (remyelination) affecting peripheral nerves.
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.
Foot-drop
MedGen UID:
88451
Concept ID:
C0085684
Disease or Syndrome
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.
Difficulty walking
MedGen UID:
86319
Concept ID:
C0311394
Finding
We walk thousands of steps each day. We walk to do our daily activities, get around, and exercise. Having a problem with walking can make daily life more difficult. . The pattern of how you walk is called your gait. A variety of problems can cause an abnormal gait and lead to problems with walking. These include: . -Injuries, diseases, or abnormal development of the muscles or bones of your legs or feet. -Movement disorders such as Parkinson's disease. -Diseases such as arthritis or multiple sclerosis. -Vision or balance problems. Treatment of walking problems depends on the cause. Physical therapy, surgery, or mobility aids may help.
Distal amyotrophy
MedGen UID:
338530
Concept ID:
C1848736
Disease or Syndrome
Muscular atrophy affecting muscles in the distal portions of the extremities.
Distal muscle weakness
MedGen UID:
355271
Concept ID:
C1864696
Finding
Reduced strength of the musculature of the distal extremities.
Split hand
MedGen UID:
67457
Concept ID:
C0221373
Congenital Abnormality
A condition in which middle parts of the hand (fingers and metacarpals) are missing giving a cleft appearance. The severity is very variable ranging from slightly hypoplastic middle fingers over absent middel fingers as far as oligo- or monodactyl hands.
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.
Hammertoe
MedGen UID:
209712
Concept ID:
C1136179
Anatomical Abnormality
Hyperextension of the metatarsal-phalangeal joint with hyperflexion of the proximal interphalangeal (PIP) joint.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
Follow this link to review classifications for Charcot-Marie-Tooth disease, type 4B2 in Orphanet.

Recent clinical studies

Diagnosis

Negrão L, Almendra L, Ribeiro J, Matos A, Geraldo A, Pinto-Basto J
Acta Myol 2014 Dec;33(3):144-8. PMID: 25873783Free PMC Article
Chen M, Wu J, Liang N, Tang L, Chen Y, Chen H, Wei W, Wei T, Huang H, Yi X, Qi M
Genomics Proteomics Bioinformatics 2014 Oct;12(5):221-7. Epub 2014 Oct 28 doi: 10.1016/j.gpb.2014.09.003. PMID: 25462154Free PMC Article

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