1) Determine the incidence of positive anti-SSA (Ro) and/or anti-SSB (La) antibodies in our population of patients with inclusion body myositis, and 2) correlate anti-SSA and/or anti-SSB antibody positivity with clinical and serologic features.

Inclusion body myositis (IBM) is a slowly progressive muscle disorder that causes significant morbidity and does not have any effective treatment.  There is substantial evidence for a primary inflammatory contribution to the disease pathogenesis, with circulating and muscle immune cell populations that are skewed towards highly differentiated T-lymphocytes, cytotoxic auto-invasive lymphocytic and plasma/dendritic cell infiltrates in the muscle, HLA-DR3 haplotype association and circulating NT5c1A autoantibodies that have high specificity.  IBM also shares an association with other inflammatory and autoimmune diseases, such as Sjögren’s disease.  Prior epidemiological studies have estimated that 6-10% of patients with IBM have evidence of Sjogren’s syndrome. There are case reports of patients with Sjogren’s syndrome-associated IBM that have demonstrated improved strength after immunosuppression.  Some of these cases are treatment responsive initially to conventional immunosuppressive therapy but then lose response, as autonomous muscle degeneration begins to occur.

INSPIRE-IBM is the largest and longest natural history study in IBM, funded through NIAMS/NIH and has enrolled 150 subjects across 13 sites in the US. Our institution is one of these sites and we have a large number of patients with IBM that follow-up in our multidisciplinary MDA clinic.  We will retrospectively analyze the rates of anti-SSA and anti-SSB antibody positivity in our population of patients with IBM.  We will also investigate associations between anti-SSA/anti-SSB antibody positivity, NT5c1A antibody positivity and clinically relevant data such as the IBMFRS or MMT12 scores.