Hypertrophic osteoarthropathy

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HPO in a German shepherd with characteristic peripheral edema[1]

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[2].

In many cases in dogs, HPO is a secondary syndrome due to chronic, space-occupying lesions of the inter-thoracic region.

The majority of cases are associated with pulmonary disease[3], most commonly pulmonary neoplasia[4].

Other diseases can result in HPO, although less commonly. These include:

- Mycobacterium spp
- Streptobacillus moniliformis (rat-bite fever)
- Dirofilaria immitis
- Spirocerca lupi
- Hepatozoon canis[7]

Early stages of the disease involve subcutaneous edema which forms as a result of periosteal hypervascularity[8]. Subsequently, thick periosteal new bone exostoses form, primarily on the appendicular skeleton.

Clinical symptoms depend on cause, but lethargy and intermittent shifting limb lameness are common, as well as conjunctivitis and episcleritis.

Blood tests usually reveal anemia, neutrophilia and elevated alkaline phosphatase.

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[9].

References

  1. University of Pennsylvania
  2. Withers SS et al (2013) Paraneoplastic hypertrophic osteopathy in 30 dogs. Vet Comp Oncol Mar 14
  3. Brodey R et al (1973) Hypertrophic pulmonary osteoarthropathy in a dog with carcinoma of the urinary bladder. J Am Vet Med Assoc 162:474
  4. Brodey R (1971) Hypertrophic osteoarthropathy in the dog: A clinicopathologic study of 60 cases. J Am Vet Med Assoc 159:1242
  5. Dunn ME et al (2007) Hypertrophic osteopathy associated with infective endocarditis in an adult boxer dog. J Small Anim Pract 48(2):99-103
  6. Seaman RL & Patton CS (2003) Treatment of renal nephroblastoma in an adult dog. J Am Anim Hosp Assoc 39(1):76-79
  7. Ewing SA & Panciera RJ (2003) American canine hepatozoonosis. Clin Microbiol Rev 16(4):688-697
  8. Holling H et al (1961) Pulmonary hypertrophic osteoarthropathy. Lancet 2:1269
  9. Lenehan, TM & Fetter, AW (1985) Hypertrophic osteopathy, in: C.D Newton, D.M. Nunamaker (Eds.), Textbook of Small Animal Orthopaedics, JB Lippincott Co, Philadelphia, PA. pp:597–601