Background Increased serum levels of B cell activating factor (BAFF) have been detected in patients with idiopathic inflammatory myopathies (IIM) , which in anti-Jo-1 positive patients correlate with serum autoantibody concentration. The correlation of BAFF expression with disease activity in IIM patients has recently been described.
Objectives To investigate serum BAFF levels in anti-PM-Scl positive patients with co-existent myositis and to assess the association with clinical disease activity in a multi-center myositis cohort.
Methods Serum BAFF levels of 37 anti-PM-Scl positive IIM patients from two European countries and in 57 healthy controls were measured using ELISA. Nineteen longitudinal serum samples with corresponding clinical data were also obtained. Clinical data were derived from the Euromyositis database (www.euromyositis.eu).
Results Serum levels of BAFF in anti-PM-Scl positive PM/DM patients were significantly higher compared to healthy controls (P=0.008), but there was no statistically significant difference between PM or DM patients (P>0.05). BAFF levels correlated with both muscular (r=0.509, P=0.002) and extramuscular disease activity (r=0.487, P=0.003). There was a negative correlation with manual muscle test (MMT8) results - increased muscle weakness thus correlated with increased serum BAFF levels (r=-0.423, P=0.025). The composite disease activity (DA) scores MITAX and MYOACT correlated positively with BAFF levels; MITAX: r=0.374, P=0.027; MYOACT: r=0.430, P=0.010. There was a correlation with disease activity (DA) of various systems: Constitutional DA (r=0.382, P=0.023), Cutaneous DA (r=0.471, P=0.004), Gastrointestinal DA (r=0.545, P=0.001) and Pulmonary DA (r=0.524, P=0.001).
Furthermore, longitudinal change (∆) in BAFF levels correlated with ∆Physician Global DA (r = 0.6834, P = 0.0035), ∆Muscular DA (r=0.786, P<0.0001), and ∆MITAX Score (r=0.672, P=0.002). Change in BAFF correlated significantly also with ∆MYOACT (r=0.698, P=0.001) and with its components: ∆Cutaneous DA (r=0.491, P=0.033), ∆Skeletal DA (r=0.588, P=0.008), ∆Gastrointestinal DA (r=0.548, P=0.015), ∆Pulmonary DA (r=0.491, P=0.039) and ∆Cardiovascular DA (r=0.471, P=0.042).
Conclusions Serum levels of BAFF are increased in anti-PM-Scl positive patients with IIM, where BAFF levels correlate with clinical disease activity assessments. Furthermore, longitudinal changes in BAFF levels over time also correlate with changes in disease activity measures. These findings indicate that BAFF is likely implicated in the pathogenesis of PM/DM. BAFF is thus a potential biomarker in IIM.
O Kryštůfková, T Vallerskog, S Barbasso Helmers, H Mann, I Půtová, J Běláček, V Malmström, C Trollmo, J Vencovský, I E Lundberg, Increased serum levels of B cell activating factor (BAFF) in subsets of patients with idiopathic inflammatory myopathies, Ann Rheum Dis 2009;68:836-843 doi:10.1136/ard.2008.091405
Acknowledgements IGA -Ministry of Health of the Czech Republic NT/12438-4.
Disclosure of Interest None Declared
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