Suspected Immune‐Mediated Myositis in Horses

Lewis, Susannah S.; Valberg, Stephanie J.; Nielsen, Ian L.

doi:10.1111/j.1939-1676.2007.tb02996.x

Cited by 44 publications

(53 citation statements)

References 33 publications

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“…Ring fibers are common in horses with myotonic dystrophy-like myopathy 21,33 but are also reported in horses with recurrent exertional rhabdomyolysis, 6 in horses with malignant hyperthermia, 1 and in horses with immune-mediated myositis. 26 Ring fibers in the current study were uncommon but were found in a horse with polysaccharide storage myopathy and in a horse with botulism, indicating that they are likely to be a nonspecific myopathic change in horses. Detection of chronic myopathic change requires sectioning to obtain transverse sections 12,40,42 and stains that emphasize fiber margins, nuclei and, in the case of ring fibers, sarcomeric arrangement.…”

Section: Discussionmentioning

confidence: 53%

Pathologic Findings in Equine Muscle (Excluding Polysaccharide Storage): A Necropsy Study

Valentine

2008

J VET Diagn Invest

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Abstract. Gross and histopathologic evaluation of skeletal muscle was performed in 229 equids (217 horses, 8 ponies, 3 donkeys, and 1 mule) 1 year of age or older undergoing postmortem examination at Oregon State University in a 2.5-year period. Animals were evaluated for grossly evident muscle lesions, and muscle samples were fixed in formalin, processed routinely, and stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) for glycogen. Muscle lesions were detected in 149 animals (65%). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses without polysaccharide storage myopathy and was the most common finding (36 animals; 15.7%). Chronic myopathic change was more common in older animals. Generalized muscle atrophy was present in 30 animals (13.1%). Myonecrosis was attributed to endotoxic injury (11 animals; 4.8%), bone fracture (8 animals; 3.5%), bacterial infection (5 animals; 2.2%), muscle rupture (3 animals; 1.3%), selenium deficiency (2 animals; 0.9%), and exertional rhabdomyolysis (1 horse; 0.4%); cause was not determined in 9 animals (3.9%). Intramyofiber protozoa were detected in 19 horses and ponies (8.3%). Denervation atrophy was detected in 14 animals (6.1%). Neoplasia involving muscle occurred in 3 animals (1.3%), injection site reactions were detected in 4 animals (1.7%), and focal lymphocytic infiltrates were found in 6 animals (2.6%). Other findings were ring fibers (2 horses; 0.9%), fiber splitting (2 horses; 0.9%), and fat infiltration (1 horse; 0.4%). Skeletal muscle lesions are common in equids examined at postmortem. Transverse sections stained with HE and PAS are invaluable when evaluating equine muscle.

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Section: Discussionmentioning

confidence: 53%

Pathologic Findings in Equine Muscle (Excluding Polysaccharide Storage): A Necropsy Study

Valentine

2008

J VET Diagn Invest

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“…[3][4][5][7][8][9][10][11][12][13][14][15][19][20][21][22][23][24][25][26] Viral infections associated with myonecrosis in the horse include equine influenza, equine infectious anemia, and equine herpesvirus 1. Figure 2.…”

Section: Discussionmentioning

confidence: 99%

“…However, a variety of infectious agents, nutritional deficiencies, toxicities, and inherited metabolic disorders can cause similar macroscopic findings in horses. [3][4][5][7][8][9][10][11][12][13][14][19][20][21][22][23][24][25][26] Several of these causative agents are listed in Table 1, and they include equine influenza virus, 8,20 Clostridium spp., 3,8,12,14,20,26 Salmonella enterica subsp. enterica serovar Infantum, 7,15 Sarcocystis fayeri, 3,8,9,12,20,26 vitamin E/selenium deficiency, 8,12,20,26 ionophore toxicity, 12,20,26 cantharidin toxicity, 12,20,26 white snakeroot toxicity, 7,12,2...…”

Section: Differential Diagnosesmentioning

confidence: 99%

Diagnostic Exercise: Equine Rhabdomyolysis

Quist

Dougherty²,

Chaffin

et al. 2011

Vet Pathol

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A 1.5-year-old Quarter Horse gelding with a history of chronic nasal discharge and leukocytosis presented with signs of increased lethargy and muscular pain. The horse quickly became recumbent and unable to rise and was euthanized due to a poor prognosis. At necropsy, severe bilateral guttural pouch empyema was observed, as well as numerous well-demarcated areas of pallor within the skeletal muscles of all major muscle groups. Polymerase chain reaction testing of the guttural pouch exudate confirmed an infection with Streptococcus equi subsp. equi, and an S. equi-associated immune-mediated rhabdomyolysis was initially considered to be the most likely diagnosis. This report briefly discusses the various etiologies that should be considered in cases of equine myopathy, and it demonstrates the complexity of these poorly understood muscular disorders.

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“…Six months prior to referral at the VTH, the referring veterinarian treated the horse for suspected immune-mediated myositis. 9 This diagnosis was based on the acute onset of lethargy, fever, anorexia, loss of muscle mass (topline and gluteal musculature), and pigmenturia. No muscle biopsy was performed to confirm the diagnosis at that time.…”

mentioning

confidence: 99%

Idiopathic Arterial Medial Calcification of the Thoracic Arteries in an Adult Horse

2008

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Abstract. A 6-year-old, gelded, Paint horse displayed clinical signs of muscle wasting and limb stiffness for a 6-month period. The horse's clinical signs abated with corticosteroid therapy, but returned upon cessation of treatment. Upon necropsy, severe lesions of aortic thickening and aortic valve rigidity were observed. Histologically, the tunica media of the aorta, coronary arteries, and pulmonary arteries were expanded by foci of elastin fiber calcification and extracellular matrix with lacunae formation. The vascular lesions are comparative to what has been described as medial arterial calcification, seen in humans suffering from chronic renal failure or diabetes mellitus. No exposure to vitamin D-containing plants or feedstuff could be documented at the time of onset or during the period of clinical signs. The current case describes dramatic lesions of arterial medial calcification of the aorta, coronary, and pulmonary arteries of undetermined cause.

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Suspected Immune‐Mediated Myositis in Horses

Abstract: IMM appears to be a distinct cause of rapid muscle atrophy, particularly in Quarter Horses that may be amenable to treatment with corticosteroids. Diagnosis is best achieved by identifying lymphocytic infiltrates in atrophied muscles.

Cited by 44 publications

References 33 publications

Pathologic Findings in Equine Muscle (Excluding Polysaccharide Storage): A Necropsy Study

Pathologic Findings in Equine Muscle (Excluding Polysaccharide Storage): A Necropsy Study

Diagnostic Exercise: Equine Rhabdomyolysis

Idiopathic Arterial Medial Calcification of the Thoracic Arteries in an Adult Horse

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