Adult-Onset Autoimmune Enteropathy Mimicking Disaccharidase Deficiency.

Adult-onset autoimmune enteropathy is a rare disorder characterized by severe diarrhea, weight loss, malnutrition, and enteric mucosal atrophy resulting from immune-mediated injury. Disaccharidase deficiencies are a group of disorders characterized by inadequate activity of disaccharidase in the small intestine, leading to impaired digestion of disaccharides and malabsorption. Here, we present a case of adult-onset autoimmune enteropathy initially diagnosed as disaccharidase deficiency based on the clinical symptoms of chronic diarrhea, weight loss, and severely reduced levels of lactase, maltase, palatinase, and sucrase in duodenal aspirates. However, follow-up duodenal biopsy revealed markedly villous blunting, goblet and Paneth cell depletion, increased crypt apoptotic bodies and lamina propria lymphoplasmacytic inflammation, leading to a revised diagnosis of autoimmune enteropathy. This case highlights the diagnostic challenges of adult-onset autoimmune enteropathy and the importance of considering it in adults with unexplained gastrointestinal symptoms. It also emphasizes the need for tissue biopsies in cases with inconclusive initial diagnostic tests. Increased awareness of these disorders and their mimickers can improve diagnosis and management, ultimately benefiting patients with these conditions.