Development of additional autoimmune diseases in a population of patients with primary Sjögren's syndrome.

BACKGROUND To investigate whether patients with primary Sjögren's syndrome (pSS) have an increased tendency to develop other autoimmune diseases. METHODS A retrospective case note review was carried out on 114 patients in whom a diagnosis of pSS had been made in a department of rheumatology from 1979 onwards. The year of diagnosis of pSS was recorded, plus the diagnosis and year of diagnosis of any other identified autoimmune disease. RESULTS Of the 114 patients with pSS, seven (6%) were male and 107 (94%) female. Mean age at diagnosis of pSS was 53 years (range 21 to 83). Patients were followed up for an average of 10.5 years (range 0 to 23). Thirty eight patients (33.3%) were diagnosed as having another autoimmune disease, while nine (7.9%) had two or more. Thirteen additional autoimmune diseases were identified. Twenty five diagnoses (51.0%) were made before the diagnosis of pSS, three (6.1%) within the same year, and 21 (42.9%) after the diagnosis. Hypothyroidism was the most common autoimmune disease (n = 16). CONCLUSIONS Although pSS is a relatively benign condition, affected individuals have an increased tendency to develop additional autoimmune diseases. Patients with pSS should be monitored on a regular basis for such diseases.