Rheumatoid arthritis as a clinical mask of primary Sjögren’s syndrome. Report of four cases

Primary Sjögren’s syndrome (pSS) is a chronic, inflammatory, autoimmune disease characterized by lymphocytes and plasma cell infiltration of exocrine glands. A typical feature of the disease is dryness of the mouth and eyes; however, pSS can also affect internal organs. Musculoskeletal complaints are the most common among non-exocrine symptoms and they can precede sicca syndrome for years. The majority of patients report a sense of pain of joints and muscles, without symptoms of arthritis. A few patients only manifest real arthritis, which can imitate rheumatoid arthritis: with long-lasting morning stiffness and symmetrical involvement of hands and feet. At the beginning of the disease, differential diagnosis of pSS and rheumatoid arthritis can be difficult, especially in pSS patients with presence of rheumatoid factor and aCCP antibodies. In this article we report on four female patients who had been treated for rheumatoid arthritis for several years before pSS was diagnosed. The paper discusses reasons for diagnostic difficulties and delay in diagnosis of pSS.