Periosteal Proliferative Polyarthritis

Introduction

Periosteal proliferative polyarthritis is a form of idiopathic inflammatory arthritis rare in dogs but recognised relatively commonly in cats.

The aetiology is uncertain, but links have been made with infections with FeLV, FIV and FeSFV (feline syncytium forming virus). It has been suggested that infection with FeLV or FIV-induced immunosuppression allows FeSFV to multiply in the joints of predisposed individuals. However there isn't an increased incidence of FeLV or FIV in affected cats.

All affected cats are infected with FeSFV, but this virus can be cultured from the joints of many normal cats too, and so the finding may be just incidental.

It occurs more commonly in young, entire or castrated, male cats less than 5 years of age.

Clinical Signs

There is an acute onset pyrexia and malaise with a stiff gait, joint effusion and joint pain.

There may be generalised muscle atrophy and lymphadenopathy.

During the more chronic phase, there is marked periosteal new bone formation, especially around the hocks and carpi, which leads to joint ankylosis in 2-8 weeks.

Diagnosis

All affected joints should be radiographed. Findings include:

periarticular soft tissue swelling

distension of the joint capsule

loss of intraarticular fat shadows

periarticular periosteal new bone formation

joint ankyolsis

osteophyte bridging of joints

coarsening of the trabecular pattern

enthesiopathies

Serial radiographs are useful to monitor the progression of the disease.

Immunological tests such as the Rheumatoid factors or the anti-nuclear antibody are negative.

Haematology and biochemistry reveal: leukocytosis, increased fibrinogen, and 50-70% of cats are FeLV positive.

Synovial fluid analysis reveals: increased volume, increased turbidity, increased white blood cell count (non-degenerate polymorphonuclear cells).

Synovial membrane biopsies can be submitted for histopathology, however the changes are not specific for the condition.

Treatment

Prednisolone is the mainstay of therapy and should be administered initially at immunosuppressive doses. The dose can be reduced to a minimal level once signs are controlled.

Additional immunosuppressive drugs can be added if the response to prednisolone alone is poor, most commonly cyclophosphamide.

Repeated synovial fluid cytology can be performed to monitor the response to treatment. A low white blood cell count indicates that treatment should be continued.

Animals should be monitored for secondary infections which can occur during treatment, and treated promptly.

Even if the drugs can be stopped, relapses often occur which require repeated treatments.

Prognosis

The overall prognosis is guarded to poor, as the condition can produce such severe joint deformity that euthanasia is indicated on humane grounds.

Periosteal Proliferative Polyarthritis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Orthopaedics Q&A 17

References

Pasquini, C. (1999) Tshauner's Guide to Small Animal Clinics Sudz Publishing

Scott, H. (2007) Feline Orthopaedics Manson Publishing

Dunn, J. (1999) Textbook of small animal medicine Elsevier Health Sciences

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