Immune-mediated polyarthritis: the role of the veterinary nurse

‘Immune-mediated polyarthritis (IMPA) is the most common form of inflammatory joint disease encountered in small animal patients’ (Stone, 2016). Before discussing what IMPA is it is important to consider the Greek origin of its title. ‘Polus’ in ancient Greek meaning ‘many or much’ and ‘arthron’ meaning ‘a joint’ allows us to appreciate that multiple joints are affected by this condition (Collins, 2022a; b). IMPA is typically an accumulation of immune complexes in the synovial fluid of a joint, which subsequently draws neutrophils into that space (Specht and Guarino, 2019). The most common presenting complaints of patients with IMPA include: fever, cyclic lethargy, anorexia and a shifting limb lameness. A retrospective study (Clements et al, 2004) identified all dogs with idiopathic IMPA presented with joint stiffness, 22 out of 39 presented pyrexic and 20 out of 39 with a lymphadenopathy. The role of the veterinary team extends beyond the initial diagnosis of the immune-mediated disease, with large involvement in clinical diagnostics, initial treatment and follow-up supportive care for our patients. Similar to the other more commonly seen immune-mediated diseases, such as immune-mediated haemolytic anaemia or immune-mediated thrombocytopenia, investigations should begin promptly to understand if the disease is from a primary or secondary cause in order to treat the patient effectively. IMPA can present as erosive or non-erosive polyarthritis, with only approximately 1% of cases reported to have erosive disease. Because of the marked reduced frequency at which erosive polyarthritis is seen in practice, the remainder of this article will predominantly focus on the non-erosive sub-categories. Commonly presenting clinical signs, diagnostics, initial treatment and follow-up care will be discussed, along with the role of the registered veterinary nurse in nursing the IMPA patient.