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Myasthenic syndrome, congenital, 25, presynaptic(CMS25)

MedGen UID:
1683288
Concept ID:
C5193027
Disease or Syndrome
Synonym: Myasthenic syndrome, congenital, 25
 
Gene (location): VAMP1 (12p13.31)
 
Monarch Initiative: MONDO:0032675
OMIM®: 618323

Definition

Congenital myasthenic syndrome-25 (CMS25) is an autosomal recessive neuromuscular disorder characterized by hypotonia and generalized muscle weakness apparent from birth. Affected individuals have feeding difficulties and delayed motor development, usually never achieving independent ambulation. Additional variable features include eye movement abnormalities, joint contractures, and rigid spine. Pyridostigmine treatment may be partially effective (summary by Shen et al., 2017). For a discussion of genetic heterogeneity of CMS, see CMS1A (601462). [from OMIM]

Clinical features

From HPO
Dysphagia
MedGen UID:
41440
Concept ID:
C0011168
Disease or Syndrome
Difficulty in swallowing.
Feeding difficulties
MedGen UID:
65429
Concept ID:
C0232466
Finding
Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Dysarthria
MedGen UID:
8510
Concept ID:
C0013362
Mental or Behavioral Dysfunction
Dysarthric speech is a general description referring to a neurological speech disorder characterized by poor articulation. Depending on the involved neurological structures, dysarthria may be further classified as spastic, flaccid, ataxic, hyperkinetic and hypokinetic, or mixed.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Decreased compound muscle action potential amplitude
MedGen UID:
908357
Concept ID:
C4230625
Finding
Reduced level of the compound muscle action potential (CMAP), which is recorded following electrical stimulation of a nerve from surface electrodes overlying a muscle supplied by that nerve.
Delayed ability to sit
MedGen UID:
1368737
Concept ID:
C4476710
Finding
A failure to achieve the ability to sit at an appropriate developmental stage. Most children sit with support at 6 months of age and sit steadily without support at 9 months of age.
Kyphosis
MedGen UID:
44042
Concept ID:
C0022821
Anatomical Abnormality
Exaggerated anterior convexity of the thoracic vertebral column.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Myopathy
MedGen UID:
10135
Concept ID:
C0026848
Disease or Syndrome
A disorder of muscle unrelated to impairment of innervation or neuromuscular junction.
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.
Generalized amyotrophy
MedGen UID:
234650
Concept ID:
C1389113
Disease or Syndrome
Generalized (diffuse, unlocalized) amyotrophy (muscle atrophy) affecting multiple muscles.
Poor head control
MedGen UID:
322809
Concept ID:
C1836038
Finding
Difficulty to maintain correct position of the head while standing or sitting.
Severe muscular hypotonia
MedGen UID:
326544
Concept ID:
C1839630
Finding
A severe degree of muscular hypotonia characterized by markedly reduced muscle tone.
Joint hypermobility
MedGen UID:
336793
Concept ID:
C1844820
Finding
The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes.
Spinal rigidity
MedGen UID:
346721
Concept ID:
C1858025
Finding
Reduced ability to move the vertebral column with a resulting limitation of neck and trunk flexion.
EMG: decremental response of compound muscle action potential to repetitive nerve stimulation
MedGen UID:
892749
Concept ID:
C4021728
Finding
A compound muscle action potential (CMAP) is a type of electromyography (EMG). CMAP refers to a group of almost simultaneous action potentials from several muscle fibers in the same area evoked by stimulation of the supplying motor nerve and are recorded as one multipeaked summated action potential. This abnormality refers to a greater than normal decrease in the amplitude during the course of the investigation.
Myopathic facies
MedGen UID:
90695
Concept ID:
C0332615
Finding
A facial appearance characteristic of myopathic conditions. The face appears expressionless with sunken cheeks, bilateral ptosis, and inability to elevate the corners of the mouth, due to muscle weakness.
Decreased fetal movement
MedGen UID:
68618
Concept ID:
C0235659
Finding
An abnormal reduction in quantity or strength of fetal movements.
Strabismus
MedGen UID:
21337
Concept ID:
C0038379
Disease or Syndrome
A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.
Limited extraocular movements
MedGen UID:
388060
Concept ID:
C1858427
Finding
Limited mobility of the eye within its socket.

Professional guidelines

PubMed

Engel AG, Shen XM, Selcen D, Sine SM
Lancet Neurol 2015 Apr;14(4):420-34. doi: 10.1016/S1474-4422(14)70201-7. PMID: 25792100Free PMC Article

Recent clinical studies

Etiology

Engel AG, Shen XM, Selcen D, Sine SM
Lancet Neurol 2015 Apr;14(4):420-34. doi: 10.1016/S1474-4422(14)70201-7. PMID: 25792100Free PMC Article
Maselli RA, Books W, Dunne V
Ann N Y Acad Sci 2003 Sep;998:18-28. doi: 10.1196/annals.1254.004. PMID: 14592859

Diagnosis

Nicolau S, Liewluck T, Shen XM, Selcen D, Engel AG, Milone M
Neuromuscul Disord 2019 Aug;29(8):614-617. Epub 2019 Jul 5 doi: 10.1016/j.nmd.2019.07.001. PMID: 31378432Free PMC Article
Engel AG, Shen XM, Selcen D, Sine SM
Lancet Neurol 2015 Apr;14(4):420-34. doi: 10.1016/S1474-4422(14)70201-7. PMID: 25792100Free PMC Article
Grand'Maison F
Can J Neurol Sci 1998 Feb;25(1):S36-9. doi: 10.1017/s0317167100034715. PMID: 9532296

Therapy

Engel AG, Shen XM, Selcen D, Sine SM
Lancet Neurol 2015 Apr;14(4):420-34. doi: 10.1016/S1474-4422(14)70201-7. PMID: 25792100Free PMC Article

Clinical prediction guides

Schmidt C, Abicht A, Krampfl K, Voss W, Stucka R, Mildner G, Petrova S, Schara U, Mortier W, Bufler J, Huebner A, Lochmüller H
Neuromuscul Disord 2003 Mar;13(3):245-51. doi: 10.1016/s0960-8966(02)00273-0. PMID: 12609506

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