Clinical, histochemical, and electron microscopic study of colonic histiocytosis.

Infiltration of the lamina propria of the mucosa of the small intestine with 'foamy' macrophages (histiocytes) which give a strongly positive cytoplasmic reaction with the periodic acid-Schiff (P.A.S.) stain is considered diagnostic of Whipple's disease (Black-Schaffer, 1949; Chears, Hargrove, Verner, Smith, and Ruffin, 1961; Farnan, 1958; Plummer, Russi, Harris, and Caravati, 1950; Sieracki and Fine, 1959); other features, such as clubbing and fusion of the villi and the presence of lipid-filled spaces in the lamina propria, are variable in degree and occasionally absent. Similar infiltration with P.A.S.-positive histiocytes is frequently observed in mesenteric lymph nodes, and less commonly in extra-abdominal tissues (Chears, Smith, and Ruffin, 1959; Enzinger and Helwig, 1963; Eyler and Doub, 1956; Farnan, 1958; Koudouris, Stern, and Utterback, 1963; Sieracki and Fine, 1959; Sieracki, Fine, Horn, and Bebin, 1960; Smith, French, Gottsman, Smith, and Wakes-Miller, 1965). These cells have been found in the lamina propria of the large bowel in several reported cases of Whipple's disease in which the diagnosis was confirmed by histological examination of other tissues (Caravati, Litch, Weisiger, Ragland, and Berliner, 1963; Fleming, Yardley, and Hendrix, 1962; Sieracki and Fine, 1959). The absence of P.A.S.-positive histiocytes in the lamina propria of the mucosa of the large bowel in proven cases of Whipple's disease has been seldom reported (Martel, Batsakis, and Bolt, 1963; Smith et al., 1965). There have been two recent reports advocating the use of rectal biopsy to diagnose this disease (Caravati et al., 1963; Fleming et al., 1962). P.A.S.-positive histio-