Selective immunoglobulin A deficiency and coeliac disease: Immune response dynamics.

OBJECTIVE: To analyse the serological immune response in paediatric patients with selective immunoglobulin A deficiency (SIgAD) and coeliac disease (CeD), focusing on immunoglobulin G antibody dynamics after starting the gluten-free diet (GFD). METHODS: Data from SIgAD patients with a CeD diagnosis, age less than 18 years, was retrospectively collected by the participating centres in this observational, multicentre, pan-european registry, conducted by the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Coeliac Disease Special Interest group. The analysis of the dynamics of normalisation of different IgG antibodies was conducted using non-parametric Kaplan-Meier curves. RESULTS: At diagnosis, there is no correlation between mucosal damage and serological levels and a small bowel biopsy is mandatory to confirm CeD in children with SIgAD. After starting a GFD IgG antibody levels decrease slowly in SIgAD patients with CeD, with 50% still serology positive after 3 years. It takes significantly longer for normalisation in those with IgG class anti-transglutaminase antibodies (IgG-TGA) baseline levels >×10 upper limit of normal (ULN). Early quantitative change in antibody levels was not predictive of final serological normalisation. CONCLUSION: Decision-making on invasive tests based exclusively on the follow-up antibody results should be avoided, given that IgG-class antibodies resolve much more slowly after commencing a GFD, especially in those patients with high baseline IgG-TGA levels.