Supplementary Material for: Macroamylasemia in a Two Year Old Boy as the First Manifestation of Celiac Disease: A Case Report

Introduction: Macroamylasemia is a rare biochemical disorder in which the amylase molecule binds to other macromolecules, most commonly immunoglobulin A or G. The increased molecular weight of this complex reduces renal excretion of the enzyme, resulting in chronically elevated serum amylase levels. It can be associated with various non-pancreatic conditions, including celiac disease. In some reported cases, macroamylasemia resolved with a gluten-free diet. We present a pediatric case in which macroamylasemia was the initial manifestation of celiac disease. Case Presentation: A two-year-old boy presented with a three-month history of abdominal pain, anemia, and, constipation. Physical examination revealed paraumbilical tenderness. Laboratory tests showed hypochromic anemia; elevated serum amylase (171 U/L); low serum iron (2.5 µmol/L); vitamin D3 deficiency (15.9 ng/mL), and low urine amylase with an amylase/creatinine clearance ratio below 1%, confirming macroamylasemia. Imaging studies were normal. HLA typing revealed the HLA-DQ2 haplotype. Celiac serology was positive for tTG-IgA (87.55 IE/mL) and EMA-IgA (1:>100). Duodenal biopsy confirmed Marsh type IIIb histology. A gluten-free diet was initiated alongside iron and vitamin D3 supplementation. Symptoms resolved within two months, accompanied by normalization of serum amylase levels and a weight gain of over 1 kg. Vitamin D3 therapy was continued until serum levels normalized. Conclusion: Celiac disease should be considered in patients with unexplained macroamylasemia, even in the absence of classical gastrointestinal symptoms. The primary treatment in such cases is a strict gluten-free diet, which can lead to the normalization of serum amylase levels when macroamylasemia is associated with celiac disease.