Dozer

History: On November 23 2009, Dozer was presented to our clinic by the Guelph Humane Society. The staff had found him to be listless, reluctant to walk or eat and had astutely observed that his limbs seemed swollen.

Physical Findings: Dozer was reluctant to walk. He had to be carried in to the clinic by one of the GHS animal care attendants and he was even reluctant to stand for long. The long bones of his front and hind limbs were quite swollen and he cried when they were palpated. The normal body temperature for dogs is between 38.0 and 39.0 degrees Celsius. Dozer’s temperature was 40.5! Dozer was given some medication to control pain and some blood work was submitted to the lab and radiographs were taken.

Laboratory Findings: Dozer’s blood work had a few abnormalities: he had a low red blood cell count (anemia) which is a common finding in rapidly growing puppies whose blood cell volume hasn’t caught up to
their size yet. He had a high white blood cell count, a sign that he had an infectious or inflammatory condition in his body (likely his bones, given all of his other signs.) And the final clue in his blood was an increase in Alkaline Phosphatase, an enzyme that increases with some liver conditions or, as in Dozer’s case, with increased bone remodelling.

Diagnostic Imaging: Dozer’s radiographs are shown on the left. Those of a normal puppy are shown for comparison on the right. The growth plates are dark (uncalcified) areas of new bone growth, indicated by the yellow arrows. In addition to growth plates, Dozers x-rays show irregular dark lesions across the bones, giving the appearance of having double growth plates (red arrows.) This pattern is typical of a growth-associated disorder called Hypertrophic Osteodystrophy.

Diagnosis: Hypertrophic Osteodystrophy (HOD). This is a rare, growth-associated bone disorder of large breed puppies with an unknown cause. Theories include vitamin C deficiency (unlikely since dogs make their own vitamin C,) and distemper virus infection but research is ongoing. It occurs more frequently in males than females and usually occurs between 3 - 7 months of age.

Prognosis: Excellent. With treatment, most puppies are more comfortable within hours of starting anti-inflammatory doses of corticosteroids. Bone changes can take months to resolve when assessed with x-rays, but most pups act and grow normally. If bowing of bones has occurred, those changes are usually permanent, but usually those changes are cosmetic only.