Is pulmonary Langerhans cell histiocytosis really rare?: A retrospective cohort study.

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare interstitial lung disease of unknown etiology, typically affecting individuals aged 20 to 40. Characteristic high-resolution computed tomography findings may obviate the need for biopsy. This study aims to raise awareness by describing clinical and imaging features of PLCH. This single-center retrospective cohort (2016-2024) included 26 confirmed PLCH patients. Demographics, smoking history, comorbidities, symptoms, lab results, 6-minute walk distance, pulmonary function tests, diffusion capacity for carbon monoxide (DLCO), and high-resolution computed tomography findings were reviewed. Median age was 46 years; 84.6% had a smoking history. Cough (46.2%) and dyspnea (53.8%) were common. Radiologically, cysts and nodules predominated. Initial DLCO was lower in dyspneic patients (P = .035). Over median 2.5 years of follow-up, pulmonary function tests and DLCO values remained stable. Early recognition of PLCH radiological features and smoking cessation are crucial. Despite limitations, these findings reinforce known patterns and highlight the need for larger, prospective studies.