Gastrointestinal dysfunction in systemic mastocytosis. A prospective study.

In 16 consecutive patients with systemic mastocytosis, we prospectively evaluated a variety of gastrointestinal functions and examined how they relate to the occurrence of gastrointestinal symptoms. Nine patients had either a duodenal ulcer or duodenitis. Hypersecretion of gastric acid was present in 6 patients, and in these patients the mean basal acid output was 20.7 +/- 4.1 mEq/h (range 14-39 mEq/h). Impaired small intestinal absorption occurred in 5 patients, although this was usually mild. The mean fractional emptying rate of liquids for all patients (14.7% +/- 2.3% per minute) did not differ from that for controls (10.7% +/- 0.6% per minute). Mean mouth-to-cecum transit time measured by breath hydrogen testing was the same among patients (87.7 +/- 6.7 min) and controls (86.7 +/- 8.0 min). Plasma histamine concentrations were increased in all patients (mean 1886 pg/ml, range 480-7450) and correlated with the basal acid output (r = 0.64, p less than 0.02) but not maximal acid output or the presence or absence of pain or diarrhea. Mean fasting plasma concentrations of motilin, substance P, and neurotensin from 6 patients did not differ significantly from controls, whereas gastrin and vasoactive intestinal peptide were significantly less than in controls (p less than 0.01). Gastrointestinal symptoms, consisting of abdominal pain or diarrhea, occurred in 80% of patients. Abdominal pain classified as dyspeptic was usually associated with acid-peptic disease of the duodenum and hypersecretion of gastric acid, whereas abdominal pain of a nondyspeptic character was not. Only in those cases of diarrhea consisting of greater than 200 g stool/day was gastric acid hypersecretion frequently found. Neither fecal urgency nor nondyspeptic pain could be accounted for by alterations of gastrointestinal transit. These results demonstrate that gastrointestinal symptoms, peptic disease, and mild malabsorption are much more common than described previously in patients with systemic mastocytosis. Furthermore, the results provide no evidence for the contention that altered gastrointestinal transit is involved in the pathogenesis of these symptoms.