Felis ISSN 2398-2950

Myopathies

Contributor(s): Laurent Garosi, David Godfrey, G Diane Shelton

Introduction

  • Myopathies are quite common in cats.
  • Signs: Muscle weakness alone or as part of a systemic illness.
  • Cause: By far the most common cause is hypokalemic myopathy Hypokalemia.
  • Ischemia associated with a thromboembolus Thromboembolism: aorta is also common
  • Other unusual causes are inherited myopathies (muscular dystrophies Muscular dystrophy, myositis ossificans Myositis ossificans, myotonia congenital Myotonia congenita, glycogen storage diseases Storage disease), idiopathic inflammatory myopathy, degenerative diseases, metabolic disorders, tumors, nutritional deficiency, paraneoplastic disease Feline cutaneous paraneoplastic syndromes, feline immunodeficiency virus disease (FIV) Feline immunodeficiency virus disease, associated myopathy and protozoal myositis ( toxoplasmosis Toxoplasmosis), endocrine myopathies (glucocorticoid myopathy, hypoadrenocorticism-associated myopathy, hyperthyroid myopathy).
  • Diagnosis: biochemistry, muscle biopsy and histopathology.
  • Treatment: treat underlying cause.
  • Prognosis: good if underlying cause identified and treated.

Pathogenesis

Pathophysiology

  • The different diseases all have a different pathogenesis.
  • There are probable genetic causes of some diseases, eg X-linked muscular dystrophy, myotonia congenita, glycogen storage disease Storage disease, Nemaline myopathy, feline muscular dystrophy with merosin (laminin a2) deficiency, hereditary myopathy of Devon Rex Devon Rex myopathy, hypokalemia of Burmese kittens Hypokalemic myopathy (Burmese) Hypokalemia    Hypokalemic myelopathy in a Burmese cat , fibrodysplasia ossificans progressiva.
  • There are underlying infectious causes in cats with myopathy associated with feline immunodeficiency virus Feline immunodeficiency virus diseaseClostridium chauvoei and Clostridium septicum, and toxoplasmosis Toxoplasmosis.
  • Polymyositis may be associated with paraneoplasia, infections or idiopathic autoimmune disease Idiopathic polymyositis.
  • Immune-mediated inflammatory myopathy is usually idiopathic. The paraneoplastic disease seen occasionally with thymoma Thymoma is probably immune-mediated.
  • The most common cause of polymyopathy is hypokalemia which causes a physiological rather than physical disease. Hypokalemia Hypokalemia may be caused by chronic renal failure Kidney: chronic kidney disease, hyperaldosteronism, thyrotoxicosis, renal tubular acidosis, excessive potassium loss, or diabetes mellitus Diabetes mellitus. It is associated with a presumably genetic disease in Burmese kittens.
  • Other electrolyte disturbances especially hyponatremia Hyponatremia (hyperadenocorticism-associated myopathy) and hypercalcemia Hypercalcemia: overview may cause some of their clinical signs by a physiological myopathy.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Volk H, Shihab N, Matiasek K (2011) Neuromuscular disorders in the cat. Clinical approach to weakness. J Feline Med Surg 13 (11), 837-849 PubMed.
  • Dickinson P J & LeCouteur R A (2004) Feline neuromuscular disorders. Vet Clin Small Anim 34 (6), 1307-1359 PubMed.
  • Braund K G (1997) Degenerative causes of myopathies in dogs and cats. Vet Med 92 (7), 608-617 VetMedResource.
  • Braund K G (1997) Endogenous causes of myopathies in dogs and cats. Vet Med 92 (7), 618-628 VetMedResource.
  • Braund K G (1997) Idiopathic and exogenous causes of myopathies in dogs and cats. Vet Med 92 (7), 629-634 VetMedResource.
  • Fascetti A J, Mauldin G E & Mauldin G N (1997) Correlations between serum creatine kinase activities and anorexia in cats. JVIM 11 (1), 9-13 PubMed.
  • Nemzek J A, Kruger J M, Walshaw R et al (1994) Acute onset of hypokalemia and muscular weakness in four hyperthyroid cats. JAVMA 205 (1), 65-68 PubMed.
  • Malik R, Mepstead F, Yang F et al (1993) Hereditary myopathy of Devon Rex cats. JSAP 34 (11), 539-546 VetMedResource.
  • Valentine B A, George C, Randolph J F et al (1992) Fibroplasia ossificans progressiva in the cat. A case report‚Äč. JVIM (6), 335-340 PubMed.
  • Dow S W, LeCouteur R A, Fettman M J et al (1987) Potassium depletion in cats - hypokalemic polymyopathy. JAVMA 191 (12), 1563-1568 PubMed.
  • Dow S W, Fettman M J, LeCouteur R A et al (1987) Potassium depletion in cats - renal and dietary influences. JAVMA 191 (12), 1569-1575 PubMed.
  • Braund K G (1986) Identifying degenerative and developmental myopathies. Vet Med 81 (8), 713-14 VetMedResource.
  • Braund K G (1986) Myopathies in dogs and cat, recognizing exogenous causes. Vet Med 81 (9), 803-13 VetMedResource.
  • Cooper B J, De Lahunta A, Gallagher E A et al (1986) Nemaline myopathy in cats. Muscle Nerve (7), 618-25 PubMed.
  • Griffin I R & Duncan I D (1979) Ischemic neuromyopathy in cats. Vet Rec 104 (23), 518-522 PubMed.

Other sources of information

  • Jones B R (1997) Congenital myotonia in related cats. Congress synopses - WSAVA, BSAVA & FECAVA, 269.


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