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.