Constipation, one of the most common GI symptoms of RTT, was present in 70.8 % of the examined RTT cohort, and it correlated with the titre of serum IgA antibodies (Spearman’s r = 0.43, p = 0.011) while the levels of serum IgA positively correlated with the ESR values (Spearman’s r = 0.462, p = 0.011). The gene discussed is CD79A; the disease is constipation disorder.