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|Title||Suspected myofibrillar myopathy in Arabian horses with a history of exertional rhabdomyolysis.|
|Publication Type||Journal Article|
|Year of Publication||2016|
|Authors||Valberg, SJ, McKenzie, EC, Eyrich, LV, Shivers, J, Barnes, NE, Finno, CJ|
|Journal||Equine Vet J|
|Date Published||2016 Sep|
|Keywords||Animals, Female, Genetic Predisposition to Disease, Horse Diseases, Horses, Male, Muscle, Skeletal, Myopathies, Structural, Congenital, Physical Endurance, Physical Exertion, Retrospective Studies, Rhabdomyolysis, Sports|
REASONS FOR PERFORMING STUDY: Although exertional rhabdomyolysis (ER) is common in Arabian horses, there are no dedicated studies describing histopathological characteristics of muscle from Arabian horses with ER.
OBJECTIVES: To prospectively identify distinctive histopathological features of muscle from Arabian endurance horses with a history of ER (pro-ER) and to retrospectively determine their prevalence in archived samples from Arabian horses with exertional myopathies (retro-ER).
STUDY DESIGN: Prospective and retrospective histopathological description.
METHODS: Middle gluteal muscle biopsies obtained from Arabian controls (n = 14), pro-ER (n = 13) as well as archived retro-ER (n = 25) muscle samples previously classified with type 2 polysaccharide storage myopathy (15/25), recurrent exertional rhabdomyolysis (7/25) and no pathology (3/25) were scored for histopathology and immunohistochemical staining of cytoskeletal proteins. Glutaraldehyde-fixed samples (2 pro-ER, one control) were processed for electron microscopy. Pro-ER and retro-ER groups were compared with controls using Mann-Whitney U and Fisher's exact tests.
RESULTS: Centrally located myonuclei in mature myofibres were found in significantly more (P<0.05) pro-ER (12/13) and retro-ER (21/25) horses than controls (4/14). Degenerating myofibres were not evident in any biopsies. Retro-ER horses had amylase-resistant polysaccharide (6/25, P<0.05) and higher scores for cytoplasmic glycogen, rimmed vacuoles and rod-like bodies. A few control horses (3/14) and significantly (P<0.05) more pro-ER (12/13) and retro-ER (18/25) horses had disrupted myofibrillar alignment and large desmin and αβ-crystallin positive cytoplasmic aggregates. Prominent Z-disc degeneration and focal myofibrillar disruption with regional accumulation of β-glycogen particles were identified on electron microscopy of the 2 pro-ER samples.
CONCLUSIONS: In a subset of Arabian horses with intermittent episodes of exertional rhabdomyolysis, ectopic accumulation of cytoskeletal proteins and Z-disc degeneration bear a strong resemblance to a myofibrillar myopathy. While many of these horses were previously diagnosed with type 2 polysaccharide storage myopathy, pools of glycogen forming within disrupted myofibrils appeared to give the false appearance of a glycogen storage disorder.
|Alternate Journal||Equine Vet J|
|PubMed Central ID||PMC4833696|
|Grant List||K01 OD015134 / OD / NIH HHS / United States |
L40 TR001136 / TR / NCATS NIH HHS / United States