Myasthenia gravis associated with thymic neoplasia in a cat

Objective: To describe acute myasthenia gravis (MG) in the postoperative period following removal of a thymoma in an adult cat. Case summary: A 6-year-old spayed female domestic short haired cat weighing 6.4 kg was referred for workup and treatment of a cranial mediastinal mass. Thoracoscopic biopsies confirmed the diagnosis of thymoma. Median sternotomy was performed and approximately 95% of the mass was surgically excised. Postoperatively the cat became remarkably weak and hypercapneic. A presumptive diagnosis of MG was made following a positive response to edrophonium injection (Tensilon test). An elevated serum acetylcholine receptor antibody level was consistent with a diagnosis of MG. Initial treatment consisted of neostigmine, followed by corticosteroids and pyridostigmine. The cat responded well to therapy. New or unique information provided: This report describes a rare syndrome of postoperative weakness due to development of MG following incomplete removal of a thymoma. Post-thymectomy weakness associated with MG has been reported in dogs and is not well described in cats.

[1]  P. Watson,et al.  Management of myasthenia gravis using cyclosporine in 2 dogs. , 2006, Journal of veterinary internal medicine.

[2]  K. Inzana.  Paraneoplastic neuromuscular disorders. , 2004, The Veterinary clinics of North America. Small animal practice.

[3]  P. Dickinson,et al.  Feline neuromuscular disorders. , 2004, The Veterinary clinics of North America. Small animal practice.

[4]  J. Posner,et al.  Immunology of Paraneoplastic Syndromes , 2003 .

[5]  A. Vincent,et al.  Unravelling the pathogenesis of myasthenia gravis , 2002, Nature Reviews Immunology.

[6]  G. Shelton.  Myasthenia gravis and disorders of neuromuscular transmission. , 2002, The Veterinary clinics of North America. Small animal practice.

[7]  J. Aarli,et al.  Titin and ryanodine receptor autoantibodies in dogs with thymoma and late-onset myasthenia gravis. , 2001, Veterinary immunology and immunopathology.

[8]  J. Coates,et al.  Treatment of a Myasthenic Dog with Mycophenolate Mofetil , 2000 .

[9]  K. Mathews.  Pain assessment and general approach to management. , 2000, The Veterinary clinics of North America. Small animal practice.

[10]  G. Shelton,et al.  Risk factors for acquired myasthenia gravis in cats: 105 cases (1986-1998). , 2000, Journal of the American Veterinary Medical Association.

[11]  J. Coates,et al.  Azathioprine therapy for acquired myasthenia gravis in five dogs. , 1999, Journal of the American Animal Hospital Association.

[12]  G. Shelton,et al.  Acquired myasthenia gravis: what we have learned from experimental and spontaneous animal models. , 1999, Veterinary immunology and immunopathology.

[13]  G. Shelton.  Myasthenia gravis: lessons from the past 10 years. , 1998, The Journal of small animal practice.

[14]  C. Vite,et al.  Acute fulminating myasthenia gravis in five dogs. , 1998, Journal of the American Veterinary Medical Association.

[15]  G. Shelton,et al.  Risk factors for acquired myasthenia gravis in dogs: 1,154 cases (1991-1995). , 1997, Journal of the American Veterinary Medical Association.

[16]  M. Day,et al.  Review of thymic pathology in 30 cats and 36 dogs. , 1997, The Journal of small animal practice.

[17]  S. Taylor,et al.  Focal myasthenia gravis as a paraneoplastic syndrome of canine thymoma: improvement following thymectomy. , 1996, Journal of the American Animal Hospital Association.

[18]  G. Ogilvie,et al.  Thymoma in dogs: 23 cases (1980-1991). , 1994, Journal of the American Veterinary Medical Association.

[19]  M. Aronsohn,et al.  Surgical treatment of thymoma in cats: 12 cases (1987-1992). , 1994, Journal of the American Veterinary Medical Association.

[20]  V. Lennon,et al.  Clinical remission following plasmapheresis and corticosteroid treatment in a dog with acquired myasthenia gravis. , 1990, Journal of the American Veterinary Medical Association.

[21]  J. C. Scott-Moncrieff,et al.  Acquired myasthenia gravis in a cat with thymoma. , 1990, Journal of the American Veterinary Medical Association.

[22]  Shin J. Oh,et al.  Edrophonium responsiveness not necessarily diagnostic of myasthenia gravis , 1990, Muscle & nerve.

[23]  V. Lennon,et al.  Myasthenia gravis in the cat. , 1988, Journal of veterinary internal medicine.

[24]  V. Lennon,et al.  Myasthenia gravis in two cats. , 1983, Journal of the American Veterinary Medical Association.

[25]  J. Dawson.  Myasthenia gravis in a cat , 1970, Veterinary Record.