Impact of Sex on Lung Function in Adult Langerhans Cell Histiocytosis

Background: Langerhans Cell Histiocytosis (LCH) is a rare histiocytic hematological disorder that frequently involves the lungs. Due to a lack of data about sex-related differences in LCH, the aim of this study is to evaluate sex-related differences in pulmonary function in a cohort of patients with LCH. Methods: We retrospectively analyzed data from 79 adult patients diagnosed with LCH. Demographic, clinical, and spirometric data were collected and compared by sex. Continuous variables were analyzed using the Mann–Whitney test and categorical variables were analyzed with the Chi-square test. Results: Out of 79 patients, 47 (59.5%) were females and 32 (40.5%) were males. Women showed significantly lower diffusing capacity of the lungs for carbon monoxide (DLCO%) and lower diffusing capacity of the lungs for carbon monoxide per unit of alveolar volume (DLCO/VA%) compared to men. Females showed a trend toward lower small airway indices, including maximal expiratory flow at 25 (MEF25%) and forced expiratory flow at 25–75% (FEF25–75%), though this was not statistically significant, while the residual volume-to-total lung capacity (RV/TLC) ratio was significantly higher in women. Among the functional parameters, DLCO% showed the highest accuracy (AUC 0.70) in the identification of lung involvement after multivariate regression analysis. Conclusions: Our findings suggest that the combination of lower gas exchange efficiency and increased peripheral air trapping secondary to small airway involvement in female patients may reflect the presence of a distinct functional LCH phenotype in women characterized by early small airway involvement and altered ventilation–perfusion dynamics, which may influence the clinical management of these patients. Furthermore, the moderate predictive value of DLCO% for lung involvement at baseline in LCH women suggests that DLCO may contribute to the detection of LCH women with lung involvement, although it should not be considered a definitive diagnostic test without a prospective and independent external validation.