Objective:To investigate changes in the expression of Cosmc and T-synthase in peripheral B lymphocytes and in serum levels of galactose-deficient IgA1 (Gd-IgA1) in patients with Henoch-Sch?nlein purpura (HSP) .Methods:From January to August 2014, 56 patients with HSP were collected from outpatient or inpatient department of dermatology and venereology in the Second Hospital of Hebei Medical University, and were divided into 4 groups, including skin type group (22 cases) , joint type group (9 cases) , abdominal type group (12 cases) and renal type group (13 cases) . Twenty healthy volunteers served as healthy controls. Real-time fluorescence-based quantitative PCR was performed to determine the mRNA expression of Cosmc and T-synthase in peripheral B lymphocytes, and a lectin-based enzyme-linked immunosorbent assay (ELISA) to detect the serum level of Gd-IgA1. Comparisons among multiple groups were performed using one-way analysis of variance or Kruskal-Wallis H test, multiple comparisons were performed using least significant difference (LSD) - t test or Nemenyi test, and correlation analysis was performed using Spearman rank correlation analysis. Results:There was a significant difference in the duration from disease onset to the clinic visit ( χ2= 26.19, P < 0.05) among the skin type group (6.27 ± 3.09 d) , joint type group (5.56 ± 3.05 d) , abdominal type group (6.75 ± 3.75 d) , and renal type group (26.23 ± 14.12 d) , and the duration from disease onset to the clinic visit was significantly longer in the renal type group than in the other 3 groups (all P < 0.05) . The Cosmc mRNA expression significantly differed among the skin type group, joint type group, abdominal type group, renal type group and healthy control group (0.849 ± 0.239, 0.767 ± 0.181, 0.719 ± 0.183, 0.459 ± 0.121, 1.146 ± 0.232, F= 23.37, P < 0.05) , was significantly lower in the 4 patient groups than in the healthy control group ( P < 0.01) , and lower in the renal type group than in the other 3 patient groups (all P < 0.01) . There was no significant difference in the T-synthase mRNA expression in peripheral B lymphocytes among the patient groups and healthy control group ( F= 1.05, P > 0.05) . The serum level of Gd-IgA1 significantly differed among the skin type group, joint type group, abdominal type group, renal type group and healthy control group ( F= 7.06, P < 0.05) . Moreover, the Gd-IgA1 level was significantly higher in the patient groups than in the healthy control group (all P < 0.05) , and higher in the renal type group than in the other 3 patient groups (all P < 0.05) . The serum level of Gd-IgA1 in the HSP patients was significantly and negatively correlated with the mRNA expression of Cosmc ( rs=-0.50, P < 0.01) . Conclusion:Decreased mRNA expression of Cosmc and increased serum levels of Gd-IgA1 were observed in patients with HSP, and there was a negative correlation between the two indices.