Abstract Introduction Sarcoidosis is a systemic disease of unclear etiology, characterized by activation of type 1 T-helper cells which trigger an inflammatory cascade of cytokines and chemokines leading to the formation of granulomas with mononuclear cells and predominant CD4 cells. Pulmonary involvement is frequent and happens in approximately 90% of patients. The spectrum of pulmonary involvement is broad, ranging from hilar lymphadenopathy, pulmonary nodules, airways disease, and in its most advanced form, fibrotic lung disease. Connective tissue diseases (CTD) are a heterogeneous group of autoimmune disorders which can involve multiple organ systems, including interstitial lung disease (CTD-ILD). CTD-ILD is characterized by the presence of autoantibodies that result in dysregulation of inflammatory pathways leading to macrophage activation, fibroproliferation, collagen overproduction, and follicular B cell hyperplasia mediated by Th17 cells. Sarcoidosis and CTD can in rare instances overlap, with one study finding a 0.3% prevalence of systemic sclerosis-sarcoidosis overlap. Accurate diagnosis of sarcoidosis-CTD overlap is complex given the rarity of this syndrome, and the variable manifestations of each disease. Furthermore, determining the prevailing condition in the pulmonary parenchyma is key to outline treatment and often times multidisciplinary discussion is required. Here we present a compilation of seven cases of sarcoidosis-CTD overlap and discuss the diagnostic and therapeutic approach. Table Discussion Here we present seven cases of sarcoidosis-CTD overlap. Concurrent CTD diseases among these cases included rheumatoid arthritis, dermatomyositis, systemic lupus erythematosus, systemic sclerosis, and mixed connective tissue disease. There was CTD-ILD in two cases, with pulmonary involvement of sarcoidosis in six cases. In the diagnosis of CTD-ILD-sarcoidosis overlap, it is key to determine whether sarcoidosis is truly present, or if the presence of granulomas is due to CTD causing granulomatous inflammation. To achieve this, tissue diagnosis and multidisciplinary discussions are often required to determine the prevailing pulmonary pathology and treatment regimen accordingly. Treatments utilized in this cohort included azathioprine, methotrexate, mycophenolate mofetil, and infliximab, some of which have a therapeutic role in both conditions. This cohort of patients is particularly well-characterized, including histopathological specimens, thorough serologic evaluation, and adequate follow-up enabling monitoring of treatment response. Sarcoidosis-CTD overlap is a rare entity that is difficult to diagnose and to treat, requiring rigorous diagnostic evaluation, involvement of multiple disciplines, and consideration of disease-specific and patient-specific factors when choosing treatments. This abstract is funded by: None
Serna et al. (Fri,) studied this question.