Pathological findings of post-anesthetic myopathy associated with type 1 polysaccharide storage myopathy in a percheron horse
Fredo, GabrielaBassuino, Daniele MariathBianchi, Matheus ViezzerDelfiol, Diego José ZanzariniBorges, Alexandre SecorunPavarini, Saulo PetinattiSonne, LucianaDriemeier, David
Background: Post-anesthetic myopathy is the most common complication associated with general anesthesia in horses. Polysaccharide storage myopathy (PSSM) is characterized by an abnormal accumulation of glycogen and glycogen-related polysaccharides in the skeletal muscle, which is categorized in type 1 (PSSM1) and type 2 (PSSM2). The purpose of this study is to report the clinical, pathological and molecular findings in a Percheron mare with post-anesthetic myopathy associated with a PSSM1. Case: A 9-year-old Percheron mare was submitted to a caesarean section due to clinical dystocia during labor. Xylazine was employed during pre-anesthesia, followed by induction with ketamine and diazepam, while anesthetic maintenance was obtained with isoflurane. The mare showed good recovery, however 24 h later, sternal recumbency and hyperthermia (41° C) were observed. The mare was euthanized, and a necropsy was performed. Samples of multiple tissues were collected and routinely processed for histology. At necropsy, segments of skeletal muscles had bilateral pale areas. The kidneys had old and recent infarcts. The heart had whitish areas in the myocardium. The brain showed focally extensive reddish areas, with flattening of gyri. Histologically, skeletal muscle fibers had in the sarcoplasm multiple homogeneous globular clear eosinophilic formations, in addition to mild hyaline necrosis. In the heart and in the kidney, there were extensive areas of acute coagulative necrosis. The brain showed marked multifocal fibrinoid degeneration of vessels and hemorrhage. Refrigerated liver samples were submitted to DNA extraction to detect mutations in the GYS1 (type 1 PSSM) and RyR1 genes (malignant hyperthermia). A positive result for a homozygous dominant mutation in GYS1 (type 1 PSSM) was observed, while the mutation responsible for malignant hyperthermia was not identified.[...](AU)
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