The association between macroamylasaemia and coeliac disease in Down syndrome with multiple autoimmune abnormalities has never been reported. A 40-year-old woman with a 15-year history of immunoglobulin A and immunoglobulin M hypergammaglobulinaemia, chronic diarrhoea, persistent mild aspartate aminotransferase (AST) elevation and anaemic syndrome was admitted to hospital because in the previous 3 months she had developed amenorrhoea, dizziness, alopecia, constipation, pallor and asthenia. Biochemical and immunological analyses showed macroamylasaemia. The patient presented clinical and intestinal histopathological features of coeliac disease. Immunological abnormalities included the presence of antigliadin, antiendomysium, antitransglutaminase, antinuclear, antismooth muscle and anti-SSA/Ro antibodies. Macroamylase resulted in a complex of amylase and immunoglobulin A. Later clinical follow-up of a gluten-free diet showed a transitory decrease in seric immunoglobulin A and macroamylase with persistent autoantibodies and AST elevation. An intestinal mucosal immune disorder could lead to coeliac disease and macroamylasaemia in a patient with Down syndrome presenting other immune alterations.