Résumé : Erdheim-Chester disease (ECD) is a rare form of non-Langerhans histiocytosis, with noncodified therapeutic management and high mortality. No treatment has yet been shown to improve survival in these patients. We conducted a multicenter prospective observational cohort study to assess whether extraskeletal manifestations and interferon-α treatment would influence survival in a large cohort of ECD patients. To achieve this goal, we thoroughly analyzed the clinical presentation of 53 patients with biopsyproven ECD, and we performed a survival analysis using Cox proportional hazard model. Fifty-three patients (39 men and 14 women) with biopsy-proven ECD were followed up between November 1981 and November 2010. Forty-six patients (87%) received interferon-α and/or PEGylated interferon-α. Multivariate survival analysis using Cox proportional hazard model revealed that central nervous system involvement was an independent predictor of death (hazard ratio = 2.51; 95% confidence interval, 1.28-5.52; P = .006) in our cohort. Conversely, treatment with interferon-α was identified as an independent predictor of survival (hazard ratio = 0.32; 95% confidence interval, 0.14-0.70; P = .006). Although definitive confirmation would require a randomized controlled trial, these results suggest that interferon-α improves survival in ECD patients. This may be seen as a significant advance, as it is the first time a treatment is shown to improve survival in this multisystemic disease with high mortality. © 2011 by The American Society of Hematology.