ABSTRACT
The major types of immune-mediated disease (hypersensitivity, autoimmunity, immunodeficiency, immune system neoplasia) are intrinsically linked, and immune-mediated disease of one type may be accompanied by one or more other immunological irregularities, expressed concurrently or sequen - tially (see Chapter 3, p. 75). For example, dogs with AIHA may subsequently (months to years later) develop other manifestations of autoimmunity (including AITP, autoimmune skin disease or lymphocytic thyroiditis), and atopic dermatitis may be complicated by other allergic disease. This chapter gives examples of multisystem or inter - current immune-mediated diseases in dogs and cats.
Pathogenesis SLE is the prototype multisystem autoimmune disease; it is at best uncommon in dogs and rare in cats. Numerous criteria for the diagnosis of canine SLE have been proposed (Table 28), but the most commonly accepted are that there should be at least two clinical manifestations of autoimmunity supported by laboratory evidence that the processes are immune-mediated, together with high titred serum ANA. Occasionally, animals may only partially satisfy these criteria; for example, by having two autoimmune processes but no serum ANA (approximately 10% of dogs with SLE are reported to be seronegative). Similarly, a syndrome of ANA-positive, immune-mediated polyarthritis and non-specific systemic illness is recognized in the GSD. Such cases may not necessarily be diagnosed as SLE, but they still fall within the same spectrum of disease and are thus considered ‘SLE-overlap syndromes’. In similar vein, two studies of canine ‘pyrexia of unknown origin’ have now concluded that a high proportion of animals with this clinical diagnosis are likely to have an immune-mediated disease and be ANA-positive.
