Serum detection of anti-cN1A is highly specific for IBM (90%–95%) compared to DM or PM (5%–10%); however; this auto-antibody has also been detected in patients with systemic lupus erythematosus (0%–20%) and Sjögren’s syndrome (0%–36%) (27). The gene discussed is NT5C1A; the disease is inclusion body myositis.