List six common causes of malabsorption.

1. Celiac disease, such as nontropical sprue (i.e., insensitivity to gluten leading to bowel dilation and intussusceptions)
2. Scleroderma
3. Whipple’s disease
4. Parasitic infestation (e.g., giardiasis, schistosomiasis)
5. Endocrine causes (e.g., VIPoma, Zollinger-Ellison syndrome)
6. infiltration (e.g., lymphoma, Waldenström’s macroglobulinemia)