Felipedia

Devon Rex hereditary myopathy

A degenerative, congenital myopathy, often called "spasticity" (albeit, erroneously), occurs in Devon rex cats and is believed to be inherited as an autosomal recessive trait. Male and female cats are susceptible and signs may be seen in young cats around 4 to 7 weeks of age but may be delayed until 12 to 14 weeks. The most consistent clinical feature is passive ventroflexion of the head and neck, which is especially noticeable during locomotion, urination or defecation. In severe cases, the chin is tucked into the sternum. Affected cats show a high-stepping forelimb gait, head bobbing, and with shoulder blades held high and the neck arched downwards. There is exercise intolerance often accompanied by progressive shortening of the stride and tremor. A "dog-begging" position is commonly observed. Some affected cats appear to have difficulty prehending and swallowing food, which may lead to upper airway obstruction. Regurgitation may be observed. Some cats have partial trismus. Clinical signs may be accentuated by concurrent illness, stress, or cold ambient temperature. Apart from variable muscle atrophy seen in some cats, neurological testing is normal.

Routine haematology and blood chemistries are normal, including serum CK levels. Radiographic and imaging studies reveal presence of megaoesophagus and oesophageal hypomotility, sometimes with gastroesophageal reflux. EMG changes are mild and include variable presence of fibrillation potentials and positive sharp waves in muscles, particularly in triceps brachii and dorsal cervical muscles. No gross changes are seen in skeletal muscles. Microscopic changes in muscle include fibre size variation associated with hypertrophic and round/angular atrophic fibres, occasional fibre degeneration/regeneration, and variable presence of internal nuclei. In muscle samples from young cats, the muscle lesions tend to be mild and variable, but become more prominent with age and/or clinical severity. There is no evidence of myositis or fibre type grouping. Dystrophin staining is normal. No abnormalities are seen in peripheral nerves, spinal cord, or brain. Mitochondrial enzyme assays in muscle are normal. The condition seems to stabilize around 9 months of age and affected cats may learn to cope with eating and drinking over time (feeding from a raised platform may be beneficial). Contractures do not occur. With adequate care, cats can thrive, although they may continue to tire easily [10]. In some cats, prognosis may be guarded due to propensity to asphyxiation and laryngospasms associated with obstruction of the larynx/pharynx with food.