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Slow-Channel Congenital Myasthenic Syndrome

SCCMS


Presentation

  • Patients typically present with fatigability and static weakness of neck, hand and finger extensors. The open-channel blockers fluoxetine and quinidine have been used as standard treatment, although the former is limited by its side effects.[ncbi.nlm.nih.gov]
  • At each delivery, she presented a transient worsening of her myasthenic symptoms.[jnnp.bmj.com]
  • Both mutations prolonged ACh-induced ion channel activations. εL78P is present in a consanguineous family and appears to be pathogenic only when present on both alleles, and εL221F shows variable penetrance in one of the two families that were identified[neurology.org]
  • Journal Article Afterdischarges in motor nerve stimulation studies help distinguish slow channel congenital myasthenic syndrome (SCCMS) from acquired myasthenia gravis (MG) We present a patient with fatigable weakness in whom afterdischarges were not[scholars.duke.edu]
Fatigue
  • Like myasthenia gravis (MG), CMS is characterized by weakness and fatigue resulting from problems at the neuromuscular junction — the place where nerve and muscle cells meet (see illustration at right).[mda.org]
  • In the less severe cases, the condition may cause drooping eyelids and fatigue, but only mildly interferes with daily life.[musculardystrophyuk.org]
  • : Pyridostigmine and 3,4-DAP Case 8 29 y old Lifelong, nonprogressive weakness in his shoulder and hip girdle muscles When walked long distance, became progressively fatigued Muscle biopsy at age 12 y “nonspecific congenital myopathy” EMG: significant[azkurs.org]
  • .  Triggered by fever, fatigue and overexertion.  Apart from these bouts, the myasthenic signs are often modest or not present. 5.  CHAT gene encoding ChAT, located on 10q11.2.  ChAT is a presynaptic protein localized in the nerve terminals, where[slideshare.net]
Episodic Weakness
  • Weakness 464 Case 73B An African American Man with Hyperthyroidism and Acute Paralysis 470 Case 74 A Boy with Large Muscles Leg Pain and Elevated Serum Creatine Kinase 472 Case 75 A Woman with Proximal Muscle Weakness Calf Hypertrophy Heel Contractures[books.google.com]
Congestive Heart Failure
  • Heart Failure 422 Case 67 An Elderly Woman with a Progressive Neuropathy 429 Case 68 A Young Woman with Difficulty Swallowing 433 Case 69 A Young Woman with Intermittent Weakness and a Positive Family History of Similar Problems 436 Case 70 A Woman with[books.google.com]
Swelling
  • Muscle Weakness 497 Case 79 A Boy Born Floppy with Severe Weakness and Later Contractures 503 Case 80 A Woman with Longstanding Weakness and Foot Deformities 510 Case 81 A Woman with Droopy Eyelids and Ophthalmoplegia 515 Case 82 A Man with Weakness and Swelling[books.google.com]
Blurred Vision
  • Bulbar symptoms including diplopia, ptosis, blurred vision, dysarthria, and dysphagia occur initially, and are followed by weakness in the upper limbs and then in the lower limbs.[neupsykey.com]
Torticollis
  • Patient I 1 , the 53-year-old father of the propositus, was suspected of having cervical torticollis at the age of 5 years and underwent surgery, which proved ineffective.[jnnp.bmj.com]
Foot Deformity
  • Deformities 510 Case 81 A Woman with Droopy Eyelids and Ophthalmoplegia 515 Case 82 A Man with Weakness and Swelling in the Neck 522 Case 83 A Woman with Muscle Pains and Dark Urine 526 Case 84 A Woman with Progressive Proximal Muscle Weakness 533 Case[books.google.com]
Leg Pain
  • […] with Proximal Weakness 448 Case 72 A Young Woman with Distal Upper Extremity Weakness 454 Case 73A A Young Man with Episodic Weakness 464 Case 73B An African American Man with Hyperthyroidism and Acute Paralysis 470 Case 74 A Boy with Large Muscles Leg[books.google.com]
Calf Hypertrophy
  • Hypertrophy Heel Contractures and Elevated Serum Creatine Kinase 480 Case 76 A Young Man with Distal Leg Wasting and Normal Sensation 484 Case 77 A Woman with Droopy Eyelids and Difficulty Swallowing 493 Case 78 A Man with Facial and Shoulder Muscle[books.google.com]
Joint Stiffness
  • It is important to try to get as much gentle exercise as possible and to continue physiotherapy to prevent complications like joint stiffness (contractures), However, it may help to use a wheelchair for any distance, to help conserve strength.[musculardystrophyuk.org]
Foot Drop
  • Case 58A A Woman with Leg Numbness Pain Weakness and Slow Nerve Conduction Velocities 372 Case 58B A Boy with Leg Weakness 375 Case 59 A Man with Hand Weakness and Numbness After Skiing 383 Case 60 A Man with Recurrent Foot Drop 386 Case 61 An Elderly[books.google.com]
  • Not able to walk 100 feet No FH of similar disease Lordotic, waddling, foot-drop gait.[azkurs.org]
Nasal Speech
  • Sometimes there are distinctive facial features such as a prominent lower jaw, high arched palate and crowded teeth (maloclusion), droopy eyes when tired, reduced eye movement with occasional double vision and unclear or nasal speech.[musculardystrophyuk.org]
Dark Urine
  • […] and Later Contractures 503 Case 80 A Woman with Longstanding Weakness and Foot Deformities 510 Case 81 A Woman with Droopy Eyelids and Ophthalmoplegia 515 Case 82 A Man with Weakness and Swelling in the Neck 522 Case 83 A Woman with Muscle Pains and Dark[books.google.com]

Workup

  • This will allow close monitoring and early intervention in the case of respiratory failure and will also expedite the diagnostic workup and initiation of therapy. 4.[neupsykey.com]
Slow Nerve Conduction Velocities
  • Case 58A A Woman with Leg Numbness Pain Weakness and Slow Nerve Conduction Velocities 372 Case 58B A Boy with Leg Weakness 375 Case 59 A Man with Hand Weakness and Numbness After Skiing 383 Case 60 A Man with Recurrent Foot Drop 386 Case 61 An Elderly[books.google.com]

Treatment

  • The patient showed marked treatment response to fluoxetine as well as quinine, a stereoisomer of quinidine, expanding the treatment options for this hereditary disorder.[ncbi.nlm.nih.gov]
  • The patient showed modest benefits from standard treatment with fluoxetine, but there was dramatic improvement when salbutamol was combined with fluoxetine.[neuroscience.ox.ac.uk]
  • In some rare cases, there is no treatment that helps. Some will need life-long medication to maintain muscle strength. In some instances, body strength may improve with treatment, but eyelid droop and eye movements do not.[musculardystrophyuk.org]

Prognosis

  • Congenital myasthenic syndromes: Natural history and long-term prognosis. Ann Indian Acad Neurol 2013;16:338-41 How to cite this URL: Jagtap SA, Abraham K, Sarada C, Nair M D. Congenital myasthenic syndromes: Natural history and long-term prognosis.[annalsofian.org]
  • Prognosis. Natural course: Appropriate management of the patient with autoimmune MG requires understanding of the natural course of the disease. The long-term natural course of MG is highly variable but generalizations are as follows.[neupsykey.com]

Etiology

  • 結節性硬化症 Tuberous sclerosis complex (TSC), unknown genetic etiology 結節性硬化症、遺伝子型不明 1 不要 有 HPS2395 HPS2396 HPS2397 HPS2398 HPS2399 HPS2400 159.[cell.brc.riken.jp]
  • Additional, smaller low-copy repeats within the BP4–BP5 segment play a role in the etiology of smaller copy number variants involving the CHRNA7 gene.[nature.com]
  • Definition/etiology : Congenital myasthenic syndromes (CMS) are a group of NMJ diseases caused by genetic defects of muscle end-plate molecules (specific proteins) involved in efficient neuromuscular transmission.[sites.google.com]
  • CMS diagnosis typically depends on a combination of factors, including clinical presentation, family history, genetic etiology, negative anti-ACh and anti-MuSK serum studies, and decremental electromyographic findings (PMID: 23622369).[invitae.com]

Epidemiology

  • Epidemiology : 2:1 male predominance. Onset: fetal life to early adulthood. Sx are present at birth in most forms but may go unrecognized until adolescence or adulthood, particularly when progression is gradual and clinical expression is mild.[sites.google.com]
  • Finally, epidemiological studies show that smoking is associated with a lower incidence of Parkinson disease. 39 Not surprisingly, nicotine and nicotinic receptor agonists are being investigated as promising therapeutic agents in the management of Parkinson[nature.com]
Sex distribution
Age distribution

Pathophysiology

  • Altogether, this mouse model provides new insight into the pathophysiology of congenital myasthenia and serves as a new tool for deciphering signaling pathways induced by excitotoxicity at peripheral synapses. Copyright 2011 Elsevier Inc.[ncbi.nlm.nih.gov]
  • Our approach suggests a robust relationship between the pathophysiology of SCS and locomotor activity.[content.iospress.com]
  • Here, we present pathophysiology and treatment of LEMS patients. Proximal weakness, depressed tendon reflexes, autonomic symptoms, and electrical posttetanic potentiation together are essential to accurately diagnose LEMS.[webview.isho.jp]

Prevention

  • If diagnosed early, CMS can be treated and prevented to some extent with medication. Almost all children with CMS will be able to walk independently and it does not affect intellect in any way.[musculardystrophyuk.org]
  • Prevention A specific diagnosis of CMS is critical as some medications that benefit one type of CMS can be detrimental in another type (Engel, A., 2007. PubMed ID:17395135).[preventiongenetics.com]
  • .  Immediate treatment of respiratory distress  Prevention of infections and of malnutrition as a result of swallowing disorders  Orthopaedic surveillance of spinal complications and retractions 33.  Cholinesterase inhibitors are efficient in all[slideshare.net]
  • Mutations in the AChR α, β, and δ subunits that reduce or prevent the expression of AChR are either lethal in embryonic life or cause marked disability and high mortality after birth.[rarediseases.org]
  • The Center for Disease Control and Prevention (CDC) recommends administration of one vial of antitoxin for adult patients with botulism as soon as diagnosis is made, without waiting for laboratory confirmation; before administration of antitoxin, consider[neupsykey.com]

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