ISSN 2398-2950      

Myasthenia gravis

ffelis

Introduction

  • Very rare disease in cats.
  • Cause: failure of normal neuromuscular transmission due to a reduction in the number of functional nicotinic acetylcholine receptor; can be congenital or acquired.
  • Signs: episodic or permanent muscular weakness, regurgitation, cervical ventroflexion, dropped jaw.
  • Diagnosis: signs, presumptive diagnosis by clinical signs and edrophonium chloride (Tensilon) challenge test, anti-acetylcholine receptor antibodies, response to treatment.
  • Treatment: pyridostigmine bromide, immunosuppressive therapy.
  • Prognosis: guarded.
    Print off the owner factsheet Myasthenia gravis Myasthenia gravis to give to your client.

Pathogenesis

Etiology

Acquired

Congenital

  • Structural or functional abnormality of acetylcholine receptors.

Pathophysiology

  • Reduction in the number of functional nicotinic acetylcholine receptor results in failure of neuromuscular transmission.
  • Acquired: aberrant immune process   →    development of heterogenous group of autoantibodies (mostly immunoglobulin class G) produced against the nicotinic acetylcholine receptor (AChR) antibodies   →    binds to the alpha-subunit nicotinic acetylcholine receptors at the neuromuscular junction   →    decreased number of functional receptors by causing endocytosis of AChR, activating complement-mediated destruction of postsynaptic muscle cell membrane near AChR, decreasing synthesis and membrane incoporation of new AChR, and directly interfering with AChR function by bound antibody.
  • Congenital: result of a single or combination of presynaptic (mutations in choline acetyltransferase gene), synaptic (mutation of the acetylcholine esterase collagen gene) or postsynaptic (mostly deficient synthesis of AChR) defect(s).

Timecourse

  • Often progress over weeks to months.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Shelton G D, Ho M, Kass P H (2000) Risk factors for acquired myasthenia gravis in cats - 105 cases (1986-1998). JAVMA 216 (1), 55-57 PubMed.
  • Ducoté J M, Dewey C W, Coates J R (1999) Clinical forms of acquired myasthenia gravis in cats. Comp Cont Educ Pract Vet 21 (5), 440-447 VetMedResource.
  • Shelton G D (1999) Acquired myasthenia gravis - what we have learned from experimental and spontaneous animal models. Vet Immunol Immunopathol 69 (2-4), 239-249 PubMed.
  • Scott-Montcrieff J C, Cook J R Jr., Lantz G C (1990) Acquired myasthenia gravis in a cat with thymoma. JAVMA 196 (8), 1291-3 PubMed.
  • Cuddon P A (1989) Acquired immune-mediated myasthenia gravis in a cat. JSAP 30 (9), 511-516 VetMedResource.
  • Joseph R J, Carrillo J M & Lennon V A (1988) Myasthenia gravis in the cat. JVIM (2), 75-79 PubMed.
  • Indrieri R J, Creighton S R, Lambert E H et al (1983) Myasthenia gravis in two cats. JAVMA 182 (1), 57-60 PubMed.

Other sources of information

  • Shelton G D (2002) Myasthenia gravis and disorders of neuromuscular transmission. In: Vet Clin North Am Small Anim Pract Ed G D Shelton, Philadelphia: W B Saunders. pp 189-206 PubMed.

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