Exercise in patients with pulmonary Langerhans cell histiocytosis: performance and mechanisms of limitation

<b>Background:</b> Pulmonary Langerhans Cell Histiocytosis (PLCH) is a diffuse cystic disease associated with reduced exercise capacity. However, the mechanisms involved in exercise limitation in PLCH are not completely understood. <b>Objectives:</b> To evaluate exercise performance and the main mechanisms of exercise limitation in PLCH. <b>Methods:</b> A cross-sectional study that evaluated 25 patients with PLCH (32% men, age 44 ± 9 years, 72% former or current smokers, with baseline dyspnea index 7 ± 3) underwent echocardiogram, six minute walk test (6MWT), pulmonary functions tests and incremental cardiopulmonary exercise test (CPET) on treadmill, with evaluation of dynamic hyperinflation. <b>Results:</b> Echocardiography suggested pulmonary hypertension in 67% of patients (tricuspid regurgitant jet velocity was 3.08 ± 0.78 m/s). The distance walked was 449 ± 93 m. FEV1 was 62 ± 21%, RV/TLC was 43 ± 11 and DLCO was 55 ± 23%. An obstructive pattern, air trapping and reduced DLCO were found in 76%, 36% and 76%, respectively. Maximal oxygen consumption was 88 ± 24% of predicted, and was reduced in half of patients. Ventilatory limitation, pulmonary hypertension (PH), dynamic hyperinflation and oxygen desaturation were identified in 36%, 23%, 66% and 73% of patients, respectively, during exercise, and most patients had more than one mechanism involved. <b>Conclusions:</b> Reduced exercise capacity is common among PLCH patients and is mainly associated with gas exchange impairment, ventilatory limitation, dynamic hyperinflation and PH, frequently with multifactorial involvement. <b>Financial support:</b> FAPESP (São Paulo Research Foundation), grant 2015/06604-0