Leucine-rich a-2 glycoprotein as a potential biomarker of idiopathic multicentric Castleman disease with pulmonary involvement: a single-center case-control study from Japan

BACKGROUND: There are no known biomarkers for monitoring disease activity in idiopathic multicentric Castleman disease (MCD) with pulmonary involvement. We investigated the utility of serum leucine-rich α2-glycoprotein levels, which reflects interleukin 6 independent inflammatory change, for monitoring disease activity in patients with idiopathic MCD with pulmonary involvement. METHODS: We retrospectively examined cases of idiopathic MCD diagnosed at Osaka University Hospital. The serum levels of leucine-rich α2-glycoprotein were compared between patients with idiopathic MCD and healthy controls. The difference in leucine-rich α2-glycoprotein levels before and after treatment (∆leucine-rich α2-glycoprotein) was evaluated with respect to the relationship with pulmonary function. In addition, the relationship between cytokine and chemokine profiles and the leucine-rich α2-glycoprotein concentration was investigated. The results were analyzed using pathway analysis. RESULTS: The leucine-rich α2-glycoprotein concentrations were significantly higher in treatment-naïve patients (n=5) than in healthy controls (n=3) (P=0.035). Further, the ∆leucine-rich α2-glycoprotein concentration was significantly correlated with ∆ percent diffusing capacity of the lung for carbon monoxide (r=−0.88, P=0.049) and tended to correlate with ∆ percent vital capacity (r=−0.68, P=0.21) although the difference was not significant for the latter association. The concentrations of chemokines and cytokines, such as CXCL9, CXCL11, CXCL1, and a proliferation-inducing ligand, were higher in the patient group than in the healthy control group. Enrichment analysis indicated that leucine-rich α2-glycoprotein could be elevated via the upregulation of chemokines in patients with idiopathic MCD using these parameters. CONCLUSIONS: Leucine-rich a2-glycoprotein may be useful for monitoring disease activity in patients with idiopathic MCD with pulmonary involvement.