Serum BAFF in Indian patients with IIM: a retrospective study reveals novel clinico-phenotypic associations in children and adults.

We studied the serum levels of B cell survival factors BAFF and APRIL in patients with idiopathic inflammatory myositis (IIM) and their relation with clinical and autoantibodies. Seventy-five patients (51 females and 24 males) with IIM (Bohan and Peter's criteria 1975) and 25 healthy adults were analyzed for BAFF, APRIL and IL-17 by ELISA, and myositis-specific and associated antibodies (MSA and MAA) using line immunoblot assay. Of the 75 patients, 59 were adults, 42 had Dermatomyositis (DM), and 17 had Polymyositis. Median disease duration was 5 (3-12) months. BAFF levels were higher in IIM than healthy controls [p = 0.001], and in children with jDM than adults [p = 0.026]. BAFF levels were higher in adults with arthritis [p = 0.018], weight loss [p = 0.007], and PAH [p = 0.004]. Among the various MSAs, lowest levels were seen in those with anti-SRP [p = 0.043]. Median follow-up duration was 145 patient years. Twelve patients relapsed, while nine were in drug-free remission. BAFF were similar between these groups. Serum APRIL levels were elevated in limited number of patients with myositis, and the levels did not differ amongst the clinico-serologic phenotypes. IL-17 levels were higher in individuals positive for anti-SRP [p = 0.028]. Serum BAFF levels are elevated in IIM, more so in children. BAFF levels may be useful as biomarker for PAH and arthritis. Anti-SRP positivity is associated with elevated IL-17 levels suggesting role in pathogenesis.