A child presents with chronic failure to thrive and steatorrhea. Biopsy of the proximal small intestine shows flattened villi and crypt hyperplasia. Using anatomical and physiological knowledge, which diagnosis and primary consequence best explain these findings?

• A. Peptic ulcer disease — localized gastric ulcers cause malabsorption in the small intestine by direct extension of acid damage into the jejunum, producing villous flattening and fat malabsorption as the primary mechanism.
• B. Celiac disease — autoimmune-mediated villous atrophy reduces absorptive surface leading to malabsorption of fats, proteins, and micronutrients causing steatorrhea and failure to thrive.
• C. Chronic antibiotic therapy — long-term antibiotics directly denature enterocyte brush-border proteins causing selective carbohydrate malabsorption only and sparing fat absorption, which contradicts the steatorrhea presentation.
• D. Irritable bowel syndrome — a functional colonic disorder that typically causes villous atrophy in the small intestine due to altered motility and is the leading cause of steatorrhea in children.

Answer: (B)