Prevalence of Pulmonary Hypertension in Patients With Pulmonary Langerhans Cell Histiocytosis: A Systematic Review and Meta-Analysis.

Pulmonary hypertension (PH) significantly affects prognosis in patients with pulmonary Langerhans cell histiocytosis (PLCH); however, reported prevalence varies substantially across studies. This systematic review and meta-analysis aimed to synthesize existing data to estimate the prevalence of PH in PLCH patients. A comprehensive literature search was performed in PubMed, Scopus, Web of Science, Cochrane Library, and Embase from inception to 2022, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Observational studies reporting PH prevalence in PLCH were included. Data extraction and quality assessment were independently conducted by two reviewers. Pooled prevalence was calculated using a random-effects model with logit transformation, and subgroup analyses explored heterogeneity by diagnostic methods, study designs, and geographical region. Ten observational studies (one prospective cohort, seven retrospective cohorts, two cross-sectional studies; total participants = 14,302) met the inclusion criteria. The overall pooled prevalence of PH in PLCH was 26.3% (95% confidence interval (CI): 17.3%-33.3%; I2 = 100%). Subgroup analysis revealed a higher prevalence in studies using echocardiography (36.3%) compared with right heart catheterization (RHC) (25.2%), and a higher prevalence observed in cross-sectional studies (40.5%) compared to prospective (5.0%) and retrospective studies (38.0%). Geographic differences between Europe and America were not statistically significant. Sensitivity analysis confirmed the robustness of the pooled estimate, and funnel plots indicated mild publication bias. This meta-analysis demonstrates a high prevalence of PH among PLCH patients. Diagnostic modality and study design contribute to substantial prevalence variability. Early screening using RHC is recommended for accurate PH diagnosis and improved clinical outcomes.