Description
Hypertrophic osteodystrophy is an extremely distressing condition which affects young rapidly growing breeds of dog. The disease causes acute pain, debilitation and death in some cases. The disease affects the metaphyseal region of the long bones, and, although any bone can be involved, the bones most often affected are those of the lower limbs (ie below the elbow in the foreleg, and below the stifle in the hindleg).
Cause
The cause of hypertrophic osteodystrophy is unknown.
Early reports that some dogs responded to vitamin C administration, despite the fact that dogs can manufacture their own vitamin C and do not have a dietary requirement for it. This lead to speculation that deranged vitamin C metabolism may be involved in the disease. However, subsequent reports suggest that vitamin C supplementation may be contraindicated because it increases serum calcium concentrations.
The observation of soft tissue calcification in some dogs suggest that mineral imbalance, overnutrition or abnormal hormonal control of calcium and/or phosphorus metabolism may be involved (e.g. mediated by vitamin D, or parathyroid hormone).
Signs
Signs of the disease can be mild with a slight lameness but they are often extremely severe with hard, painful swellings of the long bones which are warm to the touch. Severely affected dogs have a high body temperature, depression, refuse to eat and are unable to walk. This presents management problems for owners of large or giant breeds of dog.
Periods of remission can occur followed by relapse. Death can occur and euthanasia is often requested by owners with severely affected individuals. Puppies that survive this disease may have permanent skeletal deformities such as cow-hocks or angular deformity of the front legs.
The Xray
below shows the roughened outline of the long bones due to irregular new bone
deposition. There is also soft tissue swelling.
In some cases soft tissue calcification may be present as well (e.g. the aorta, lining of the heart (endocardium), kidneys or lungs.