Importace of monoclonal immunoglobulin in Sjögren’s syndrome

Background: Sjögren’s syndrome is the second most common systemic autoimmune disease after rheumatoid arthritis, RA, with a prevalence of about 0.5% in the general population. It occurs primarily in perimenopausal women (at a ratio of women to men of 9: 1) Sjögren’s syndrome is characterized by lymphocytic infiltration to exocrine glands. The specific autoantibodies of this syndrome are against Ro (SSA) and La (SSB). B cell dysfunction occurs in patients with Sjögren's syndrome. B lymphocyte cells produce monoclonal immunoglobulin heavy and light chains addition to producing Ro (SSA) and La (SSB). Up to 25% of patients in this situation are associated with antibody production. This study aimed to evaluate the prevalence of monoclonal immunoglobulin in patients with primary Sjögren's syndrome. Methods: 31 patients with primary Sjogren's syndrome diagnosed according to the American College of Rheumatology (ACR) criteria referred to Rheumatology Clinics of Firoozgar Hospital, Tehran, during first six months of 2016, were studied. Clinical examinations and tests carried out. We analyzed serum monoclonal immunoglobulins by immunofixation electrophoresis (IFE) on agarose gels with specific antisera to IgG, IgM, IgA, and κ and λ chains. The IFE was performed with a Helena immunofixation agarose kit (Helena Laboratories, Beaumont, TX, USA) following the manufacturer's recommended procedure. The measures of Anti-Ro, anti-La, rheumatoid factor (RF), antinuclear antibodies (ANA) with immunofluorescent method, complete blood count (CBC) with differential by peripheral blood smear, an erythrocyte sedimentation rate with western green tube, dip stick urine analysis, urine specific gravity (SG) with Refractometer (Mesu Lab Instruments Co., Guangzhou, China), turbidimetry serum complement, and the complement CH50 with ELISA were done. Results: Most of (87%) patients were female. The mean age of patients was 45.32±12.02 years. The majority of the patients (94%, 29 cases), ocular sign was observed. Xerostomia were common in 84% cases (n=26). Arthralgia/arthritis and submandibular enlargement were common 48% and 19% of patients, respectively. Lymphadenopathy, lung involvement and parathyroid, each was prevalent in 16% of patients. Vasculitis in 13% and Raynaud's phenomenon in 6% of the patients were common. Liver and kidney involvements with the lowest prevalence, each was prevalent in 3% (1 person) patients. RF and the erythrocyte sedimentation rate (ESR) were abnormal in 22.58% and 12.90% of patients, respectively. The immunofluorescent antinuclear antibody (ANA or FANA) pattern, C3 and C4 complements levels were abnormal in 16.12%, 12.90% and 6.4% of patients, respectively. In 29% (n=9), monoclonal antibodies were higher than normal. IgG, IgM and IgG, were abnormal in 19.3% (n=6), 6.4% (n=2) and 3.3% (n=1), respectively. Conclusion: Monoclonal immunoglobulin levels in patients with primary Sjogren's syndrome increases. To achieve more definitive and reliable results, this study should be repeated with larger sample size and at different times.