Serum immunoglobulin free light chain assessment in rheumatoid arthritis and primary Sjogren's syndrome.

BACKGROUND: B cell activation may result in an increased secretion of immunoglobulin free light chains (FLCs) in autoimmune diseases. OBJECTIVE: To analyse serum FLC levels in patients with rheumatoid arthritis and in those with primary Sjögren's syndrome (pSS). PATIENTS AND METHODS: Blood samples were collected from 80 healthy blood donors, 50 patients with rheumatoid arthritis and 139 patients with pSS. Serum FLC level was measured using a new quantitative immunoassay. RESULTS: Mean (standard error (SE)) serum kappa and lambda FLC levels were significantly higher in patients with rheumatoid arthritis and in those with pSS than in controls (kappa : 18.9 (1.1) and 16.3 (1.4) v 10.5 (0.4) mg/l, p<0.001 and p = 0.001, respectively; lambda: 16.7 (1.2) and 19.3 (1.5) v 11.6 (0.6) mg/l, p<0.001 for both). 18 (36%) patients with rheumatoid arthritis and 31 (22.3%) patients with pSS had abnormal serum FLC levels (increased kappa or lambda levels and abnormal ratio of kappa:lambda). Serum kappa and lambda levels were correlated with other B cell activation markers in both diseases. FLC levels increased with disease activity, because, unlike total gammaglobulin and immunoglobulin G levels, they were significantly correlated with Disease Activity Score 28 in patients with rheumatoid arthritis (p = 0.004 for kappa, p = 0.05 for lambda) and with extraglandular involvement in pSS (p = 0.01 for kappa, p = 0.04 for lambda). CONCLUSION: FLC levels are increased and correlate with disease activity in patients with rheumatoid arthritis and in those with pSS, two diseases in which increased risk of lymphoma could result from persistent B cell activation and disease activity. Further studies are required to determine whether FLC assessment could represent a relevant biomarker for response to treatment (especially B cell depletion) and for the risk of lymphoma in autoimmune diseases.

Anti-pm/scl antibodies in connective tissue disease: Clinical and biological assessment of 14 patients.

INTRODUCTION: Anti-PM/Scl antibodies (Anti-PM/Scl) represent a rarely encountered type of antinuclear antibodies. They have mainly been reported in association with idiopathic inflammatory myositis - systemic sclerosis overlap syndromes (also called scleromyositis or sclerodermatomyositis) but also with polymyositis, dermatomyositis and systemic sclerosis without features of overlap syndromes. Studies concerning characteristics of patients with anti-PM/SCl are rare and include small numbers of patients. PATIENTS AND METHODS: Retrospective review of clinical and biological characteristics of 14 patients with anti-PM/Scl in two University Hospitals: one in Belgium (Erasme Hospital, Bruxelles) and one in France (Hautepierre Hospital, Strasbourg). RESULTS: Seven patients were identified in Erasme and 7 in Strasbourg: 5 with systemic sclerosis-(dermato)myositis overlap syndromes, 4 with dermatomyositis, 1 with polymyositis, 3 with systemic sclerosis, 1 with primary Sjögren's syndrome. The most frequently observed clinical characteristics (85% of patients) were: pulmonary interstitial disease and arthralgia or arthritis. No patient of our series died or developed cancer (mean follow-up:6.1 years). CONCLUSIONS: Our study failed to identify an homogeneous clinical pattern in patients with anti-PM/Scl, except for 2 characteristics shared by 85% of the patients. This lack of homogeneity is in agreement with preceding literature. We confirm the favourable prognosis associated with the presence of anti-PM/Scl, despite the high incidence of interstitial pulmonary disease. The absence of cancer associated with presence of anti-PM/Scl represents a partial explanation. Finally, we report herein the second case of primary Sjögren's syndrome associated with anti-PM/Scl.