VIPoma with expression of both VIP and VPAC1 receptors in a patient with WDHA syndrome.

We report a case of VIPoma in a 72-year-old female patient who presented with excessive diarrhea, severe hypokalemia, and acidemia. She had been referred to our hospital three times because of severe diarrhea. No primary tumor site was found by conventional techniques, including contrast-enhanced CT and MRI, angiography, endoscopy, and positron emission tomography (PET), but a tumor was subsequently found in the head of the pancreas by octreotide scanning. Her diarrhea diminished dramatically after octreotide treatment, while her diarrhea has ceased without the therapy of octreotide at the first admission in the course of 2 years of her disease. Immunohistochemial analysis of the excised tumor tissue revealed the expression of both vasoactive intestinal peptide (VIP) and VIP and pituitary adenylate cyclase-activating peptide 1 (VPAC1) receptors. This is the first case report of a VIPoma that immunostains for VIP and VPAC1 receptors and indicates that abundant VIP produced by VIPoma might inhibit its growth and reduce VIP secretion via the VPAC1 receptor in vivo.