Abstract
Objective: To report a remarkable case of respiratory bronchiolitis associated with interstitial lung disease (RB-ILD) and Langerhans Cell Histiocytosis (LCH). Case Report: Male patient, 57 years old, obese, sedentary, with smoking load of 80 packs per year. During a routine consultation, he underwent a chest computed tomography (CT) scan that revealed small nodular opacities of nonspecific aspect, in addition to the diagnosis of centrilobular pulmonary emphysema. After 8 months, the patient presented to a pulmonologist with persistent cough and no changes in the physical examination. A new CT was performed, revealing multiple nodular opacities with irregular contours diffusely affecting the parenchyma of both lungs, predominantly in the upper and middle lobes, with suspicion of secondary neoplastic involvement. A lung biopsy revealed a nodular inflammatory infiltrate, with irregular borders, in a peribronchiolar and subpleural distribution, composed of pigmented histiocytes and lymphoid aggregates in the midst of fibrosis. The adjacent parenchyma revealed respiratory bronchiolitis. Immunohistochemical examination revealed positivity for CD1a+ cells in some nodules. The findings were compatible with RB-ILD and LCH, these being diseases of rare etiology that present on imaging exams similar to other lung diseases. Final Considerations: Since these are rare conditions, it is necessary that they be properly investigated to avoid misdiagnosis and inappropriate treatment.