- Sjögrens syndrome in humans is an idiopathic autoimmune disease characterized by lymphoplasmacytic infiltration and destruction of lacrimal and salivary glands, resulting in reduced secretion from these glands and the clinical presentation of keratoconjunctivitis sicca (KCS) and xerostomia (dry mouth). In addition there is often dryness of other mucosal surfaces (nasal, trachea, bronchial, vaginal) and of the skin. This form of disease is sometimes termed primary Sjögrens syndrome.
- Approximately one half of affected humans have concomitant rheumatoid arthritis or one of the other autoimmune connective tissue diseases, and in this instance the disease may be termed secondary Sjögrens syndrome. Lymphoplasmacytic infiltrates may occur in other organs (kidney, lung, lymph node, muscle) and some patients go on to develop lymphoma (generally ß cell lymphoma). The disease has a distinct gender predisposition (90% of cases occur in females) and the mean age of onset is 50 years. There are specific serological changes typified by hypergammaglobulinemia and the presence of autoantibodies including antinuclear antibody (ANA; present in 70% of patients), rheumatoid factor (RF; present in 90% of patients) and autoantibodies specific for salivary antigens (present in 50% of patients). A small proportion of patients (5%) develop lymphocytic thyroiditis (hypothyroidism). Medical treatment is with immunosuppressive drugs and artificial tears, with symptomatic therapy for dry mouth (eg oral hygiene, frequent water intake).
- Although KCS [Keratoconjunctivitis sicca] is well-documented in the dog, true Sjögrens-like syndrome is rare. Only two dogs satisfying the criteria for diagnosis of this disease have been formally reported in the literature (with one further report as part of a case series), however there may be some overlap syndromes in which dogs presenting with apparently uncomplicated KCS have serological changes related to connective tissue disease (eg ANA and RF), or in which dogs with KCS have another concomitant autoimmune disease such as hypothyroidism , rheumatoid arthritis , diabetes mellitus , chronic active hepatitis or autoimmune skin disease . The two affected canine patients were part of an experimental breeding colony of dogs with systemic lupus erythematosus (SLE) .
- It has been suggested that canine Sjögrens-like syndrome may be under diagnosed. Dogs presenting with primary KCS have been shown to have subclinical histopathological changes in salivary gland tissue, and some dogs with KCS that are evaluated for parotid duct transposition also have a degree of xerostomia. One study of 50 dogs with KCS identified 10 animals as having evidence of xerostomia.
- Clinical features consistent with KCS and xerostomia should be present in definitive cases of Sjögrens-like syndrome. The clinical appearance may reflect secondary inflammatory or infectious processes occurring subsequent to lack of protective ocular or oral secretion. Signs related to polyarthritis, hypothyroidism, diabetes mellitus, gastrointestinal or liver disease, or immune-mediated skin disease may also be present.
- The main differential diagnoses for Sjögren's-like syndrome are uncomplicated KCS, or KCS concomitant with other immune-mediated disease processes that does not match the diagnostic criteria for Sjögren's-like syndrome (ie 'overlap syndromes').