Blood MMP-7 and TNF-α levels as potential prognostic biomarkers for adult pulmonary Langerhans cell histiocytosis

The natural history of pulmonary Langerhans cell histiocytosis (PLCH) is unpredictable. Therefore, the identification of prognostic biomarkers for PLCH represents a major goal for better management of patients. The aim of this study was to evaluate the levels of various blood mediators in PLCH patients at diagnosis and explore their relationships with forced expiratory volume in one second (FEV₁) outcomes. We used multiplex immunoassays to measure at diagnosis the serum concentrations of thirty mediators in patients with stable vs. declining FEV₁. Multivariable-adjusted logistic regression models, accounting for matched variables (age, sex, and daily tobacco consumption), were used to compare concentrations between patients stratified on the basis of their FEV₁ values. Nine patients with declining FEV₁ profiles over time who had an available blood sample at the time of PLCH diagnosis were paired with 16 patients whose FEV₁ profiles remained stable over a median follow-up of 3.6 years [IQR 2.2-5.1]. The levels of two biomarkers, TNF-α and MMP-7, were significantly greater in patients with a decreased FEV₁ than in those with a stable FEV₁ in the univariable analysis after adjustment for matching variables. The median serum levels of TNF-α were 137 [75-358] pg/mL in the declining FEV₁ group and 60 [45-92] pg/mL in the stable FEV₁ group (p = 0.032). Similarly, the median MMP-7 levels were 16344 [13318-18000] pg/mL and 11555 [9796-12495] pg/mL, respectively (p = 0.047). There was a negative correlation between FEV₁ values and MMP-7 levels (rho = -0.65, p = 0.001) but not with TNF-α levels (rho = -0.33, p = 0.14). TNF-α and MMP-7 levels are potential prognostic blood biomarkers in PLCH.