Ultrastructural changes in the duodenal mucosa induced by ingested histamine in patients with chronic urticaria.

Histamine in food may be responsible for some cases of food intolerance. We previously demonstrated disturbances in the metabolism of ingested histamine in patients with chronic urticaria (CU) and proposed that this could be related to increased intestinal permeability to histamine. The present study was undertaken to look for ultrastructural changes in the intestinal tract that might explain this abnormality. We examined duodenal biopsies from seven patients with CU before and after intraduodenal administration of histamine (120 mg). Five subjects had clinical symptoms (diarrhea, urticaria, headache, accelerated heart rate, and drop in blood pressure) within 1 h of duodenal histamine challenge (DHC). Ultrastructural changes, including edema of the interstitial tissue, enlargement of the basal intercellular spaces, slight congestion of the endothelial cells, and pericapillary edema, were observed in six subjects 45 min after DHC. In all the biopsies, the epithelium was normal, and the tight junctions were not modified by DHC. This morphologic study demonstrates that histamine can induce edema in the basal intercellular spaces of the duodenal mucosa and in the submucosa without evident change in the integrity of intercellular junctions. The most plausible route for histamine to have taken would appear to be an intracellular one.