Histopathological findings in horses with and without clinical signs of rhabdomyolysis with special reference to polysaccharide storage myopathy

Abstract

Objective of the study was to assess histopathological changes in horses with a clinical history of exertional rhabdomyolysis (ER) with special reference to polysaccharide storage myopathy and to compare histopathological findings in horses with and without a clinical history of ER. In total 39 muscle samples were collected, from horses with a history of repeated episodes of exertional rhabdomyolysis (test group, 10 horses) and from horses without clinical signs of muscular disorders in their history (control group, 29 horses). Frozen muscle samples were stained with haematoxylin and eosin and periodic acid-Schiff with and without amylase digestion. Histopathologic changes (amylase resistant polysaccharide, subsarcolemmal glycogen, intracytoplasmic masses, subsarcolemmal vacuoles, fibre size variation and internal nuclei) were evaluated. There was a statistically significant difference between groups in the presence of subsarcolemmal amylase sensitive glycogen deposits (P ≤ 0.0001), the risk ratio was 5.22. Statistically significant differences between groups were not found regarding the presence of intracytoplasmic masses, subsarcolemmal vacuoles, amylase resistant polysaccharide, fibre size variation and internal nuclei. Presence of amylase resistant polysaccharide within muscle fibres of apparently healthy horses could be a manifestation of different phenotype expression of PSSM but also the insufficient specificity of this diagnostic criterion.

Effect of head and neck position on outcome of quantitative neuromuscular diagnostic techniques in Warmblood riding horses directly following moderate exercise

“…The significant increase in LDH activity indicated that leakage from muscle fibres was present in HNP4, 5 and 7. In addition, CK activity increased Ն2-17 times in individual horses in HNP4, HNP5 and HNP7 whilst increases Ն50-250% are considered pathological (Harris 1998;Ludvikova et al 2008). This is in agreement with former studies concluding that of CK, ASAT and LDH activities, LDH activity appeared to be the most sensitive marker of increased workload (Krzywanek et al 1996;Wijnberg et al 2008) or myopathy (Wijnberg et al 2003a).…”

“…The significant increase in LDH activity indicated that leakage from muscle fibres was present in HNP4, 5 and 7. In addition, CK activity increased ≥2–17 times in individual horses in HNP4, HNP5 and HNP7 whilst increases ≥50–250% are considered pathological (Harris 1998; Ludvikova et al . 2008).…”