Abstract
Rheumatoid arthritis (RA) and diffuse Bronchiectasis (dBr) are very strongly associated, yet the biological significance of this comorbidity remains unexplained. Risk factors for the coexistence of RA and dBr include age, male gender, longer RA disease duration, anti-CCP antibodies, genetics and undetectable circulating mannose-binding lectin (uMBL). Higher morbidity and mortality occur in these comorbid disorders. Undetectable MBL is associated with coexistent RA and dBr. Very low MBL (<200 ng/mL) is also associated with poorer outcomes in all cause diffuse Bronchiectasis. Undetectable MBL may contribute to RA pathogenesis in the context of dBr, due to a permissive effect for chronic infection, which may lead to a break in immune tolerance and in turn auto-immune disease expression. Lung infection in untreated and treated persons with autoimmune diseases should be a major concern for physicians. Chronic infections associated with bronchiectasis may trigger and/or exacerbate auto-immune disease and complicate therapy. Even in patients with no known pulmonary pathology, lung infections are common and often serious, especially in the context of corticosteroid use and probably to a moderate extent with the use of biologic DMARD therapy. Amongst well recognised and newly emerging risk factors for lung infection in RA+dBr, uMBL warrants further examination, both to confirm and more clearly define its role in the pathogenesis of infection and to explore scope for MBL repletion, with a view to preventing infection and improving survival.