Serum Osteoprotegerin, RANKL, and Dkk-1 Levels in Adults with Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease of unknown etiology with a strong evidence of immunological dysfunction secondary to cytokine dysregulation.This study aimed to evaluate serum receptor activator of nuclear factor κB ligand (RANKL), osteoprotegerin (OPG), and Dickkopf-1 (Dkk-1) levels in adult patients with LCH at various stages of the disease.This was a cross-sectional study in an adult LCH cohort followed for 12.2 ± 2.1 yr.The study was conducted in an outpatient clinic.Twenty-five adult patients with a definitive LCH diagnosis and 50 matched controls participated in the study.Early morning, fasting, venous sampling was conducted in all subjects.We compared RANKL, OPG, and Dkk-1 serum levels between patients and controls, as well as their association with disease parameters.Serum OPG levels were significantly higher (3.0 ± 0.2 vs. 1.7 ± 0.1 pmol/liter; P0.001), whereas RANKL/OPG ratio was significantly lower (0.201 ± 0.041 vs. 0.471 ± 0.072; P = 0.02) in LCH patients compared to controls. Both higher OPG (adjusted odds ratio, 3.431; 95% confidence interval, 1.329-8.924) and lower RANKL (adjusted odds ratio, 0.144; 95% confidence interval, 0.034-0.605) levels were independently associated with LCH in logistic regression analysis, after adjustment for all other parameters. Dkk-1 did not differ among patients and controls.Adults with LCH have high serum OPG levels and low serum RANKL levels. In contrast with other disorders involving the skeleton, serum Dkk-1 levels are similar between LCH patients and controls.