The CRP levels in patients with IgG4-RD do not increase significantly[37]; however, high CRP levels can be a hallmark of IgG4-related periaortitis/periarteritis.[38] The median CRP level of IgG4-related periaortitis/periarteritis is 6.72 (2.14–24.65) mg/dL.[39] In this case, the CRP levels was 8.33 mg/dL; therefore, we misattributed this elevation to IgG4-related periaortitis. Here, CRP is linked to polyarteritis nodosa.