Feline post-anesthetic death: A complication of a rare disease

Amanda Mansz

Animal Health Laboratory, University of Guelph, Guelph, ON.

AHL Newsletter 2022;26(3):27.

A young male Russian blue cat was presented to the AHL for postmortem following an unexpected death shortly after recovery from neuter surgery.  The cat had a long-term history of abnormal gait.  Prior to surgery, blood work revealed elevations in AST and ALT.  Gross postmortem findings included a severely thickened diaphragm (Fig. 1A), and hypertrophy of the muscles of the dorsal neck and shoulders (Fig. 1B).  Microscopic review of skeletal muscle tissue from several locations showed myocyte degeneration, necrosis and regeneration with marked variation of myofiber diameter, and extensive endomysial and perimysial fibrosis (Fig. 2B).  In addition, some hind limb muscle bundles had massive, widespread myocyte necrosis characterized by sarcoplasmic eosinophilia, fragmentation, vacuolation, and nuclear pyknosis (Fig. 2A).  Based on gross and histological findings, a diagnosis of feline muscular dystrophy (also called feline hypertrophic muscular dystrophy) was made.

Feline muscular dystrophy is a very rare condition and there are very few published reports.  Depending on the genetic variation, this congenital condition often affects young male cats when X linked.  These cats often have a history of limb stiffness or gait abnormalities, and chronic elevations of ALT and AST due to leakage from damaged muscles.  Anaesthetic and post-anaesthetic death is well documented with this condition.  Dystrophin-deficient cats can develop a “malignant hyperthermia-like syndrome” associated with restraint, stress, or general anesthesia.  The massive necrosis seen microscopically in the hind limb skeletal muscles in this case may be representative of this phenomenon.

Confirmation of the type of muscular dystrophy (dystrophin deficient vs. α-dystroglycan deficiency vs. laminin deficiency) requires immunohistochemical/immunofluorescent staining for these skeletal muscle proteins, which was not pursued in this case.   AHL

Figure 1. Feline muscular dystrophy.  A. Severe multifocal thickening of the diaphragm (black line and oval); normal diaphragm thickness (white line and oval).  B. Hypertrophy of the muscles over the dorsal neck.

Figure 2. Feline muscular dystrophy skeletal muscle histologic lesions. A. Massive hind limb myocyte necrosis characterized by sarcoplasmic vacuolation, fragmentation, hypereosinophilia and nuclear pyknosis. H&E stain. B. Marked variation of myofiber diameter with alternating atrophied and hypertrophied fibers, regional endomysial and perimysial fibrosis, and foci of mineralization. H&E stain.

References

1. Remmers G, et al. Postanesthetic death in a cat with myopathy. Vet Pathol. 2015;52(1):186-188.

2. Gaschen, F, Gaschen, L, Seiler, G. Lethal peracute rhabdomyolysis associated with stress and general anesthesia in three dystrophin-deficient cats. Vet Pathol. 1998;35(2):117–123.