Context: Autoimmune polyglandular syndrome type I (APS I) is characterized by multiple endocrine gland failures, with other manifestations such as gastrointestinal (GI) symptoms.

Objective: To study the histopathologic and immunologic findings in the GI mucosa of a patients with typical features of APS I, malabsorption and pernicious anemia.

Design and Patient: Biopsies from the GI tract of a patient with APS I were immunostained with chromogranin for GI endocrine cells (GIECs). Blinded slides were graded for numbers of endocrine cells. Normal gastric mucosa was exposed to the patient's serum to test for circulating anti-GIEC and anti-parietal cell antibodies using indirect immunofluorescence.

Setting: Departments of Pediatric and Medical Gastroenterology in an academic medical center.

Results: The patient's GI mucosa demonstrated absence of GIECs throughout, including gastric gastrin-secreting cells, and her laboratory tests for serum gastrin levels were low normal. Both GIECs and parietal cells were absent in her gastric corpus. The patient's serum contained anti-GIEC antibody but no anti-parietal cell antibody.

Conclusions: These observations suggest that GIECs in APS I are subject to an autoimmune destruction that can cause widespread GIEC loss. This could explain the GI dysfunctions that are often noted in the syndrome including malabsorption and atrophic gastric changes with pernicious anemia. We also hypothesize that absence of gastric parietal cells may result mainly from hypogastrinemia that is mainly the loss of gastrin-secreting cells rather than from immune-mediated destruction of parietal cells like that seen in the atrophic gastritis associated with adult-onset pernicious anemia.