Hypertrophic osteoarthropathy (HPO) is a paraneoplastic progressive, symmetric and bilateral periosteal disease of dogs characterized by bilaterally symmetrical, nonedematous soft tissue swellings affecting primarily the distal portions of all four limbs.
In many cases in dogs, HPO is a secondary syndrome due to chronic, space-occupying lesions of the inter-thoracic region.
Other diseases can result in HPO, although less commonly. These include:
- Infective endocarditis
- Pulmonary abscess
- Neoplasia - e.g. renal nephroblastoma, malignant mesenchymoma, schwannoma, anal sac adenocarcinoma
Early stages of the disease involve subcutaneous edema which forms as a result of periosteal hypervascularity. Subsequently, thick periosteal new bone exostoses form, primarily on the appendicular skeleton.
This insidious disease, often misdiagnosed as arthritis in the early stages, ultimately affect all the bones of the limbs, resulting in severe disability.
With treatment of the primary condition, the secondary reaction noticably regresses in 3 – 4 months.
- University of Pennsylvania
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