Hypertrophic Osteodystrophy (HOD)

Patty Khuly

Summary

This relatively uncommon disease of swelling, painful bones is primarily seen in large breed pups (usually between 2 and 6 months of age) whose rapid growth means lots of constant cellular change in the body’s skeleton. Such a lightning-speed laying down of new bone during growth is currently suspected to influence the resulting bony swelling the disease is known for. But the truth is that we don’t really understand the exact cause-and-effect relationship between rapid growth and Hypertrophic Osteodystrophy (HOD).

Distemper virus infection or other viral infections, vaccines (especially the distemper virus vaccine) and bacterial infections may be involved as the trigger for this disease process.

Luckily, this is a self-limiting disease, one which resolves by itself over a few weeks’ time. Genetic predisposition is considered a factor as certain breeds are found to be affected with greater frequency.

Symptoms and Identification

In HOD, the bones swell. They become painful to the touch (especially at the ends of the long bones in the forelimbs) and dogs may be lame on one or more limbs. Fever is often present and the affected bones may feel swollen and hot. Lethargy and inappetance is common to these dogs while, diarrhea, tonsillitis, pneumonia and thickening of the pads of the feet have also been associated with it.

Young, large breed pups between 2 and 6 months are the typical sufferers. Some will experience a brief episode and dispense with all symptoms while others will undergo weeks of heavy pain.

To diagnose HOD, veterinarians will take X-rays of suspected cases. The findings in these usually include a darker line within the ends of the long bones where there should be none. This line indicates death of the bone in this area and is a clear indication of the presence of a process like HOD. This finding, along with the pain, fever, age and size of the dog conspire to secure the diagnosis.

Affected Breeds

Young, fast-growing, large breed dogs like Great Danes, Boxers, German shepherds and Weimaraners are most commonly diagnosed with HOD. Because of the relatively higher incidence in these breeds, a hereditary influence is suspected.

Breed Risk Relative to Mixed Breed Dog
Boxer 18.4x
German Shepherd Dog 9.6x
Golden Retriever 5.4x
Great Dane 189.8x
Irish Setter
14.3x
Labrador Retriever 5.9x
Weimaraner 21.4x

Estimates based on claims paid by Embrace Pet Insurance

Treatment

Treatment for this self-limiting condition primarily revolves around pain relief. Treatment is largely supportive, consisting of IV fluid therapy for dogs with high fevers and pain medication for all. Anti-inflammatory drugs such as the aspirin-like NSAIDs (like carprofen and meloxicam) or corticosteroids (like prednisone) and non-narcotic opiates (like tramadol) are commonly prescribed. In more severe cases, narcotics (like hydromorphone and fentanyl) will be employed as well. Sometimes antibiotics will be considered for those pets whose symptoms appear to be related to an infection.

Unfortunately, the sometimes unbearably severe pain means that dogs may be euthanized in lieu of treatment.

Veterinary Cost

Because most dogs “grow out of it,” treatment with medications lasts only a few days to weeks. This can range from a manageable low-hundreds condition (including the cost of diagnosis) to a higher hundreds rate for those who require more expensive medications.

Nonetheless, the cost of this kind of treatment can be substantial if the pups are more severely affected. In these cases they may need to be hospitalized for the entire duration of their illness for continuous IV fluid therapy and intensive pain relief. Because this can run into the thousands of dollars for a severe case, euthanasia is considered a reasonable option for those who cannot afford this high cost of care.

Prevention

Since we don’t yet understand this disease, prevention is a fuzzy subject for veterinary medicine. Do we refuse to vaccinate for distemper in the event that this may be related to HOD? Not if distemper virus itself, endemic as it is in the US, may also be a factor––and a deadly disease in its own right. That’s why preventing infections and spaying and neutering all affected dogs to head off any possible passing down of this trait is the mainstay of HOD prevention.