Comparative Neuromuscular Laboratory

NEUROMUSCULAR CASE OF THE MONTH - SEPTEMBER 2003

ALERT! Spinal muscular atrophy: An Emerging Inherited Disorder of Maine Coon Cats
Contributed by Dr. John Fyfe, Michigan State University and Dr. Diane Shelton, University of California, San Diego

A slowly progressive neuromuscular disorder of Maine coon cats has recently been identified. The disorder is an autosomal recessive degeneration of motor neurons that results in weakness and severe muscle atrophy first evident around 4 months of age. In September of 1997 a breeder of Maine coon cats placed a world wide web posting on a listserver of Maine coon breeders describing a disorder in two kittens she had produced. Another breeder recommended contacting Dr. John Fyfe at Michigan State University because the disorder sounded similar to one he previously described in Norwegian forest cats and for which a DNA-based carrier test had been developed. Since that time several affected cats, both male and female, have been studied. Prior to onset of clinical signs between 15 and 17 weeks of age, the kittens appear clinically normal, alert and responsive. Initial abnormalities include pelvic limb weakness and fine generalized tremor. Affected kittens may lose the ability to jump by 5-12 months of age and walk with a pelvic limb sway. Stance is abnormal with hocks nearly touching and hind feet pointing out at an angle from midline of 30-40°. Hyperesthesia may also be identified over the lumbar spine. The weakness and muscle wasting is slowly progressive; however, not incompatible with an acceptable quality of life for a variable number of years as indoor pets.

The goal is to create a definitive carrier test with the aim of elimination of this disorder from the breeding population of Maine coon cats, so affected kittens are no longer produced. To achieve this goal cooperation of breeders and owners of affected cats will be required. If an owner or breeder of a Maine coon cat believes they have an affected animal with clinical signs similar to that described above, Dr. Fyfe would be happy to consult with them or their veterinarian on reaching a definitive diagnosis. They may contact Dr. Fyfe at (517) 355-6463 (ext 1559) or by email at fyfe@cvm.msu.edu. Dr. Fyfe specializes in the characterization of inherited disorders in dogs and cats. His website is http://www.msu.edu/unit/mic/facpages/fyfe.html