Objective: To investigate serum levels of B-cell activating factor (BAFF) in patients with myositis and correlate these to autoantibody profile, clinical phenotype and treatment.
Methods: BAFF levels in sera from 49 patients with dermatomyositis, 44 with polymyositis, 6 with inclusion body myositis and 30 matched controls were measured by enzyme-linked immunosorbent assay (ELISA). Specific autoantibodies were detected by line-blot and western blot assays.
Results: Serum levels of BAFF were significantly higher in patients compared to healthy controls (p=0.003). Patients with anti-Jo-1 autoantibodies had higher BAFF levels than control individuals (p<0.003) or patients without any specific autoantibodies (p<0.05). Patients with dermatomyositis had higher BAFF levels compared to polymyositis (p<0.05). Patients with interstitial lung disease (ILD) had higher BAFF levels than patients without ILD (p<0.05) or controls (p<0.01) but this could be explained by presence of anti-Jo-1 autoantibodies. BAFF levels correlated with serum CK (rs=0.365, p=0.0005) but not with CRP levels. A negative correlation of BAFF levels with glucocorticoid daily dose for all patients (rs=-0.292, p=0.003) and with cumulative glucocorticoid doses in early myositis cases (rs=-0.659, p=0.0002) was recorded.
Conclusion: Our finding of elevated serum levels of BAFF in myositis patients with described phenotypes together with the correlations between levels of BAFF and CK and a negative correlation with dose of glucocorticoids, indicate that BAFF could be a potential therapeutic target in such cases.