Exostosis

Cartilagenous exostosis is an uncommon condition in which nodules of cartilage, with or without bone, spread in the growth plate of various bones. Multiple exostosis, also called multiple cartilagenous exostoses or MCE, is a hereditary disorder transmitted by an autosomal dominant gene and characterized by multiple growths near the ends of long bones, ribs, and vertebrae of the spinal cord. These growths practically can be seen on any bone except the skull. The genetic abnormality results in a defect at the ends of the bone at an early age. Benign, bony outgrowths develop often capped by cartilage. A small number undergo tumor-like transformation.

Formation of bone exostosis are common findings in dogs affected by American canine hepatozoonosis and contribute to the painful sensation of stiffness of infected dogs.³ In cats, MCE has been associated with feline leukemia virus (FeLV).

Signs of Exostosis

Affected animals show forelimb lameness and are in great pain. The disease occurs predominantly in young dogs and adult cats. The masses continue to grow until the skeletal maturation is complete. Dogs with MCE may be young adults (more than 1 year old) by the time a mass or masses result in clinical signs of disease. Some dogs may develop neurologic dysfunction at an older age

Treatment with non-steroidal anti-inflammatory drugs is not effective and usually unnecessary unless it causes serious neurological complications. If the mass compresses the spinal cord, a surgical procedure will be performed to remove the growth.

The prognosis depends on the number, location and surgical accessibility of the masses and is usually good if it does not transform into a cancerous tumor. Continuous or renewed growth past the time of skeletal maturity is considered to be a malignant condition. Dogs with preexisting MCE may develop chondrosarcoma, the second most common primary tumor of bone in humans and dogs.

The disease is considered aggressive in cats and has a poor prognosis.

References:
1. Small Animal Paediatric Medicine and Surgery By Giselle Hosgood, Johnny D. Hoskins, Jacqueline Davidson, Julie A. Smith.
2. A Practical Guide to Canine and Feline Neurology. Curtis W. Dewey
3. Encyclopedia of arthropod-transmitted infections of man and domesticated animals. M. W. Service, R. W. Ashford