Whipple’s disease. This is a rare systemic illness that involves the small intestine mucosa but also may have low-grade fever, arthralgias, lymphadenopathy, and CNS symptoms (confusion, loss of memory, vision abnormalities, and symptoms referable to involvement of one or more cranial nerves). The GI symptoms are primarily those of malabsorption similar to sprue; with steatorrhea, weight loss, abdominal pain, and hypoalbuminemia (due to loss into the GI tract). Diagnosis currently involves biopsy of the duodenal mucosa, which contains many PAS stain-positive macrophages in the mucosa. A bacillus-type infection has been postulated on the basis of electron micrograph findings, but no organism has been cultured that could be proven to be the responsible agent. Recently, two groups of investigators using nucleic acid probe methods have identified a bacillus that appears to be a gram-positive member of the actinomyces family, tentatively named Tropheryma whippelii. Culture has not yet been possible and this discovery still must be definitively established.