ObjectiveTo learn the serum immunoglobulin G4 (IgG4) level in patients with pemphigus vulgaris (PV) in the active phase by detecting the IgG4 concentration in the patients with PV. MethodsWe collected the serum samples from patients with active-phase PV (including acute-onset and chronic active phases) between April and December 2014. The serum IgG4 level was detected by immuno-scatter turbidmetry, and the difference of serum IgG4 level between PV patients and normal subjects was assessed by Student's t-test. ResultsThirty-two patients with pemphigus vulgaris in the active phase were enrolled for this study, among whom 22 (including 8 males and 14 females) had normal serum IgG4 level, 8 (including 3 males and 5 females) higher and 2 (including 1 male and 1 female) lower. Compared with normal subjects, the average level of serum IgG4 in PV patients was not significantly different (P>0.05). The serum IgG4 level of acute-onset and chronic active PV patients was (1.015±0.825) g/L and (1.058±1.133) g/L, respectively, with no significant difference (P>0.05). ConclusionThe serum IgG4 level of patients with pemphigus vulgaris in the active phase can be normal, higher or lower. And there is no obvious difference in the serum IgG4 level between acute-onset and chronic active PV patients.