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Hypertrophic Osteodystrophy and Panosteitis

This condition, also known as HOD, is most commonly seen in rapidly growing large or giant breed puppies. Thankfully, it is an uncommon disorder. To understand the disease process, we first need to understand the anatomy of the bones of a growing puppy. The long bones of the body have four main parts during the growth phase. The shaft of the bone is called the diaphysis. During growth, the ends of the bones are separated from the diaphysis by cartilage. This is called the physis. As growth and development occur, the cartilage turns to bone, this is where osteochondrosis occurs (an abnormal ossification or hardening of the cartilage). On the diaphysis side of the physis is the zone of growth, called the metaphysis. On the other side of the physis, adjacent to the joint space is the epiphysis. HOD is a disease that attacks the bones at the metaphysis. The bone becomes softer than normal and in response, the body lays down new bone along the periosteum (thick fibrous covering of the bone). There is often swelling at the joints because of this bony proliferation, and pain. This disease usually attacks the bones of the forelimb (radius and ulna) and sometimes the hindlimb (tibia). In rare cases, more extensive involvement of the skeleton occurs (jaw, paws, shoulder blade, and ribs). In addition to obvious pain, high fevers often accompany this disease.

So, what causes this nasty disease? Well, we don’t really know. In some cases, especially in Weimaraners, it has been associated with the administration of a modified live virus vaccine, particularly the Distemper vaccine.

All large and giant breed dogs are at risk, but this disease does seem to be most common in Dobermans, German Shepherds, Great Danes, Labrador Retrievers, and Weimaraners (to name a few).

Diagnosis can be made by labwork (which is not really specific for the condition) and radiographs (x-rays), which do tend to be specific for this disease. Another way to differentiate this from another orthopedic disease that strikes young growing puppies (panosteitis) is by localizing the pain to the metaphyseal regions. We will discuss panosteitis below.

Treatment involves pain management and control of the fever. Antibiotics are sometimes prescribed if a bacterial infection is suspected. Restricting physical activity and ensuring adequate food intake are important.

Permanent deformity of the bones may result from this disease. The milder the disease, the milder the deformity of the bones. This disease may recur in susceptible puppies during their rapid growth phase (3-7 months of age).
Panosteitis
This disease can be somewhat difficult to distinguish from HOD, as the symptoms of pain and fever often are present with panosteitis too. Remembering the parts of the growing bone from above, this disease affects the diaphysis and pain is limited to the shaft of the bones, not the joints. The bone itself is not abnormal in this disease, but the fatty bone marrow inside the bone. The bone marrow begins to degenerate and following this degeneration, the bone inside the shaft becomes inflamed, degenerates, and then is replaced with new bone.

So, what causes this? Again, we don’t really know. It may have some genetic or hereditary components, may be stress related, or may be related to Von Willebrand’s disease. Von Willebrand’s disease is an abnormality of the blood clotting mechanism due to an abnormality of the von Willebrand factor, which affects the ability of platelets to stick together and clot the blood.

Male German Shepherds are over-represented in the incidence of this disease, but other breeds also seem to suffer from panosteitis at an increased incidence. These include Great Danes and Basset hounds.

Diagnosis can be made by labwork (it is important to run a von Willebrand factor test) and radiographs.

Treatment is similar to that of hypertrophic osteodystrophy and includes rest and pain relief.

There are not any potential bone deformities that can develop from panosteitis, but the disease may recur during the growth of the puppy (usually 5-12 months of age).

Please note that this information does not replace professional veterinary care. It is solely for educational purposes. Your pet's medical condition should be evaluated by a veterinarian before any medical decisions are implemented. If there is a potentially life-threatening emergency involving your pet, take your pet to a veterinarian or veterinary facility immediately.

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