Histology of intestinal Whipple's disease revisited. A study of 48 patients.

Whipple's disease is an infectious disorder with intestinal and extra-intestinal manifestations. We reinvestigated the intestinal histology in a series of 48 patients (10 females, 38 males; mean age 56.5 years, standard deviation of the mean +/- 11.2 years). A total of 126 biopsy samples, obtained prior to, during, and after therapy, were evaluated by light microscopy. In 43 patients (90%), histology was consistent with common descriptions, while it was uncommon in 3 patients (6%), and non-diagnostic in 2 patients (4%). During treatment, several alterations occurred. Apart from a continuous decrease in PAS-positive macrophages, the pattern of mucosal infiltration changed from diffuse to patchy. Moreover, the cytological aspects of PAS-positive macrophages changed substantially, and this change was used to propose four different subtypes. Initially, subtype 1 macrophages predominated (74%), but showed a gradual decrease within a few months of therapy. After 15 months, subtype 3 and subtype 4 macrophages predominated (< 80%). In 7 of 9 patients followed over long periods some subtype 3 or subtype 4 macrophages persisted. It is concluded that at diagnosis and during treatment the intestinal histology of Whipple's disease is heterogeneous. A few PAS-positive macrophages commonly persist at long-term follow-up. This and other features suggest the presence of a persistent immune defect.