Association between anti-α-1,4-D-polygalacturonic acid antibodies and Henoch-Schönlein purpura in children

OBJECTIVE: To investigate the relationship between anti-α-1,4-D-polygalacturonic acid (PGA) antibodies, particularly immunoglobulin (Ig)A, and Henoch-Schönlein purpura (HSP) in children. METHODS: This observational case–control study investigated PGA-IgA, PGA-IgG, and PGA/PGA-IgA circulating immune complex (PGA/PGA-IgA CIC) in paediatric patients with HSP versus controls. Children with HSP were also evaluated for food specific IgG and food intolerance. Between-group differences in anti-PGA antibodies were analysed. RESULTS: Serum PGA-IgA and PGA-IgG levels were significantly increased in patients with acute HSP (n = 251) versus those with urticaria (n = 48), acute respiratory infections (n = 95), surgical controls (n = 53) and neonates (n = 92). PGA/PGA-IgA CIC levels were also significantly higher in the acute HSP group versus surgical control and neonate groups. Levels of PGA/PGA-IgA CIC and PGA-IgA were significantly correlated (r = 0.997), and PGA-IgA showed high diagnostic specificity for HSP. No statistically significant differences were observed in PGA-IgA and PGA-IgG between various degrees of food intolerance in children with HSP. CONCLUSION: Increased anti-PGA antibodies, particularly PGA-IgA and PGA/PGA-IgA CIC, were significantly associated with acute HSP in children. Food intolerance was not found to be associated with increased anti-PGA antibodies in children with HSP.