Pulmonary Langerhans Histiocytosis: an uncommon cause of interstitial pneumonia in a patient with Sjögren syndrome.

Sjögren syndrome is a chronic, systemic, and autoimmune disorder that targets exocrine glands by remarkable B cell hyperactivity. Eventually, it is associated with extra-glandular clinical manifestations that affect essentially any organ system, including pulmonary involvement. Interstitial lung disease is one of the most serious pulmonary complications, and the early diagnosis is essential to initiate a prompt therapy. On the other hand, Sjögren syndrome could present concomitantly with several rheumatologic diseases such as systemic lupus erythematosus or rheumatoid arthritis. Pulmonary Langerhans Histiocytosis is a rare clonal proliferative disease characterized by pulmonary involvement by cells phenotypically similar to Langerhans cells. We describe the case of a nonsmoker 62-year-old woman with Sjögren syndrome who presented concomitantly a Pulmonary Langerhans Histiocytosis mimicking a pulmonary complication of its Sjögren. Fortunately, she had a well response to corticosteroids and azathioprine regimen. The aim of the paper is to emphasize the importance of the good differential diagnosis related to the pulmonary involvement. To the best of our knowledge, this is the first description of these two entities in the literature.