What is Hypertrophic osteopathy?

Hypertrophic osteopathy, commonly abbreviated HO, is a disease where the dog suffers from bilateral, symmetrical soft tissue swelling of its lower legs. Hypertrophic osteopathy can also cause periosteal new bone formation. The joints are not affected. During the early stages of Hypertrophic osteopathy, the blood flow to the lower limb is increased dramatically.

Hypertrophic osteopathy is always the result of some other underlying health problem, such as cancer or tuberculosis. The exact cause of Hypertrophic osteopathy is still not understood. A majority of the cases are found in dogs suffering from secondary or primary lung cancer. It is also known that a dog that has had a limb amputated due to bone cancer is at higher risk of developing Hypertrophic osteopathy. Spirocercosis and heartworm infections can also cause Hypertrophic osteopathy in dogs.

Hypertrophic osteopathy (HO) is known under a wide range of different names, including hypertrophic osteoarthropathy (HOA), hypertrophic pulmonary osteopathy (HPO), hypertrophic pulmonary osteoarthropathy (HPOA), pulmonary osteoarthropathy (POA), osteoporosis deformans, achropachia, and Marie's disease.

Hypertrophic osteopathy symptoms in dogs

Hypertrophic osteopathy can lead to symptoms such as lameness and reluctance to walk in a dog. If you look at the lower legs of an effected dog, you can often see symmetrical firm soft tissue swellings. The limbs tend to be warmer than normal, and many dogs are very sensitive to touch.

The veterinarian will use x-rays to confirm the diagnosis. In early stages of Hypertrophic osteopathy, there is soft tissue swelling. During later stages, perisosteal new bone development have started, which can be smooth as well as uneven. The vet can also use radiographs to find out the underlying cause. 

Dogs at risk of developing Hypertrophic osteopathy

All dog breeds can suffer from Hypertrophic osteopathy, but it is more common in large breeds. Based on case reports, the Boxer dog have a higher risk of developing Hypertrophic osteopathy compared to other breeds. This is probably caused by the higher occurrence of primary lung cancer and bone cancer in this breed. The German Shepherd also has an elevated risk of developing Hypertrophic osteopathy.

Hypertrophic osteopathy is more common in female dogs than in male dogs. This is probably related to the fact that mammary carcinomas can lead to Hypertrophic osteopathy.

When small and medium sized dogs get Hypertrophic osteopathy, they are usually middle aged or older, since cancers are less common in young dogs. Large and giant dog breeds are however prone to developing bone cancers while still fairly young and vets are therefore quite frequently presented with young, large dogs with Hypertrophic osteopathy.

Hypertrophic osteopathy treatment for dogs

The ideal treatment for hypertrophic osteopathy depends on the underlying cause. The bony changes can regress if the vet manages to cure the underlying health problem, e.g. remove a lesion from the chest. When hypertrophic osteopathy is caused by heartworm infestation or primary lung tumours, surgery is a good option. In some situations, the only thing the vet can do is to provide palliative care using pain killers suitable for dogs.  Dogs suffering from hypertrophic osteopathy due to secondary lung cancer have a very poor prognosis and euthanasia is normally better choice than surgery.

Skeletal and muscular disorders in dogs: (click for more info)
Canine hip dysplasia
Congenital vertebral anomalies in dogs
Craniomandibular osteopathy in dogs
Elbow dysplasia in dogs
Hypertrophic Osteodystrophy in dogs
Hypertrophic Osteopathy in dogs
Legg-Calvé-Perthes syndrome in dogs
Luxating patella in dogs
Masticatory muscle myositis in dogs
Masticatory Muscle Myositis (MMM) and Extraocular Myositis (EOM) in dogs
Osteoarthritis in dogs
Osteochondritis Dissecans in dogs
Panosteitis in dogs
Spondylosis in dogs