Macroglobulinemia and small intestinal disease. A case report with review of the literature.

Involvement of the gastrointestinal tract in macroglobulinemia is exceedingly rare. We describe a patient with IgM biclonal immunoglobulin disorder associated with diffuse lymphoplasmacytic infiltration of the small intestine. This chronic illness was characterized by diarrhea, steatorrhea, and intestinal pseudo-obstruction. Full-thickness biopsy specimens of the jejunum showed stunted and fused villi, giardiasis, and a widespread cellular infiltrate in the lamina propria extending through the muscularis mucosae into the submucosa and muscular layers. The infiltrate had a cytologically benign appearance that was shown to be polyclonal by immunochemical stains. Intestinal vacuolated plasma cells were occasionally observed in electron microscopic study. The patient has not developed the features of Waldenstrom's disease on a clinical follow-up of 14 years.