Primary Sjögren syndrome and development of another autoimmune rheumatic disease during the follow-up

Background: Primary Sjögren syndrome (pSS) is a chronic autoimmune disease with its main target being exocrine glands, and is the connective tissue disease more frequently associated with other autoimmune diseases. The aim of this study was to assess the frequency of another autoimmune rheumatic disease (ARD) developed in primary Sjögren syndrome (pSS) patients and to describe it's clinical, serological and histologic characteristics.

Materials and methods: This is a retrospective cohort study. Data of patients with pSS diagnosis (American-European criteria 2002), included in the GESSAR database (Grupo de Estudio Síndrome de Sjögren, Sociedad Argentina de Reumatología) were analyzed. The development of a second ARD was registered during the follow up.

Results: 681 patients were included, 94.8% female. The mean age was 54 (SD 14) years and mean age at diagnosis of 50 (SD 13) years. The mean follow-up was 4.7 (SD 4.9) years; 30 patients (4.41%, CI 95%: 3.1-5.7) developed a second ARD during the follow up, incidence rate was 9.1/1000 patients-year (IR 95%: 5.8-12.4/1000 patients-year), the most frequent being rheumatoid arthritis (RA). 96% out of these 30 patients had xerophthalmia, 86.2% xerostomia, 92% positive Schirmer test, 88.24% positive Rosa Bengala test, lisamine green or Ocular Staining Score, 81.2% positive unstimulated salivary flow, 82.1% Ro(+) and 33.33% La(+). Minor salivary gland biopsy had been performed in 14 of the 30 patients, 12 with positive results. There were no statistically significant differences respect baseline characteristics when comparing the patients who developed another ARD to the ones that did not.

Conclusions: Of all the patients analyzed, 4.4% presented another ARD during their follow-up. It is important to be aware of this, to make an early and proper diagnosis and treatment of our patients.