Among the 43 anti-GBM patients with MPO-ANCA, the patients with positive P2-IgM had a higher level of serum C reaction protein (CRP) [151.0, 93.2–162.0 vs. 11.4, 4.2–52.0 mg/l, P = 0.002]. The gene discussed is CRP; the disease is glioblastoma.