Serum
gastrin levels exceeding 1000pg/ml (normal, <100) usually raise the suspicion for a
neuroendocrine tumor (NET) that secretes
gastrin. Rarely, such elevated
gastrin levels are seen in patients with
pernicious anemia which most commonly is associated with autoimmune
gastritis (AG). AG can occur concomitantly with other autoimmune disorders including
lymphocytic colitis (LC).
Gastrin stimulates enterochromaffin-like cells which increase
histamine secretion.
Histamine excess can cause
diarrhea as can bacterial overgrowth or LC. We present a 57-year-old woman with
diarrhea, sporadic epigastric
pain, and bloating. She also had a history of
interstitial cystitis and took
pentosan polysulfate and
cetirizine. She had no history of
ulcers, renal impairment or
carcinoid syndrome. Fasting serum
gastrin was 1846pg/ml. Esophagoduodenal gastroscopy and biopsies revealed chronic
gastritis and a pH of 7 with low stomach
acid. Serum
gastrin and plasma
chromogranin A were suggestive of a
gastrinoma or NET.
Pernicious anemia was unlikely. Imaging studies did not reveal any
tumor. Random colonic biopsy was compatible with LC, possibly explaining her
diarrhea, although we also considered excessive
histamine from elevated
gastrin, bacterial overgrowth, and
pentosan polysulfate which can cause
diarrhea and be misleading in this setting, pointing to the diagnosis of
gastrinoma. At 4year follow-up in 2012, fasting serum
gastrin was 1097pg/ml and the patient asymptomatic taking only
cetirizine for nasal
allergies. This case illustrates that
diarrhea may be associated with very high serum
gastrin levels in the setting of chronic
gastritis, LC, and
interstitial cystitis (pentosan use), without clear evidence for a
gastrinoma or NET. If no history of
ulcers or liver
metastases is present in such cases, watchful observation rather than an extensive/invasive and costly search for a NET may be justified. Considering the various forms of polyglandular syndrome, this may represent a variant and we here provide an algorithm for working up such patients, while also reviewing literature on the intertwined relationship between the immune and endocrine systems.