Periodic acid-Schiff-negative granulomatous lymphadenopathy in patients with Whipple's disease. Localization of the Whipple bacillus to noncaseating granulomas by electron microscopy.

The diagnosis of Whipple's disease in a 58-year-old man was based on the finding of periodic acid-Schiff (PAS)-positive foamy macrophages on duodenal biopsy and demonstration of the typical bacilliform bodies by electron microscopy. The patient also had generalized peripheral lymphadenopathy with lymph node biopsy showing PAS-negative noncaseating granulomas. Electron microscopic examination of the lymph node specimen demonstrated a small number of typical bacilliform bodies with localization specifically to the granulomas in the lymph node. This finding of bacilliform bodies within PAS-negative noncaseating granulomas has not been reported previously. Localization of the Whipple bacillus specifically to noncaseating granulomas suggests that some patients with the disease may manifest a delayed hypersensitivity reaction to the bacillus.