Late-Onset Gastrointestinal Manifestations of Multiple Endocrine Neoplasia Type 2B (MEN2B) - Diffuse Ganglioneuromatosis Causing Megacolon

Sep 28, 2026

Multiple endocrine neoplasia type 2B (MEN2B) is a rare autosomal dominant disorder caused by RET protooncogene mutations, classically associated with medullary thyroid carcinoma (MTC), pheochromocytoma, and gastrointestinal ganglioneuromatosis. Gastrointestinal symptoms, including constipation and megacolon, typically occur in infancy or childhood; late-onset presentation is rare. A 66-year-old woman with MEN2B presented with absolute constipation, abdominal distension, nausea, and vomiting. Imaging showed marked colonic dilatation without obstruction, leading to emergency total colectomy with end ileostomy and histopathology-confirmed diffuse ganglioneuromatosis, highlighting timely surgical intervention across age groups.

LanguageEnglish

CategoryHealthcare

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Pages7

Reading Time18 min

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Abstract

Introduction

Case Presentation

Imaging and Diagnosis

Treatment and Outcome

Pathology and Histology

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Review began 11/03/2025 Review ended 12/01/2025 Published 12/03/2025 © Copyright 2025 Rana et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0. , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited. DOI: 10.7759/cureus.98366 Open Access Case Report Late-Onset Gastrointestinal Manifestations of Multiple Endocrine Neoplasia Type 2B (MEN2B) : Diffuse Ganglioneuromatosis Causing Megacolon Maheen Rana 1 , Saddam Hussain 1, Samira Osman 2 , Paul Anant 3 1. General Surgery, Our Lady of Lourdes Hospital, Drogheda, Drogheda, IRL 2. Pathology, Our Lady of Lourdes Hospital, Drogheda, Drogheda, IRL 3. General Surgery, Portiuncula University Hospital, Ballinasloe, IRL Corresponding author: Maheen Rana, [maheenrana123@gmail.com](maheenrana123@gmail.com) Abstract Multiple endocrine neoplasia type 2B (MEN2B) is a rare autosomal dominant disorder caused by RET protooncogene mutations, classically associated with medullary thyroid carcinoma (MTC), pheochromocytoma, and gastrointestinal ganglioneuromatosis. Gastrointestinal symptoms, including constipation and megacolon, typically present in infancy or childhood ; late-onset presentation is rare. We report a 66-yearold woman with MEN2B, previously treated with total thyroidectomy for MTC and bilateral adrenalectomy for pheochromocytoma, who presented with absolute constipation, abdominal distension, nausea, and vomiting. Imaging demonstrated marked colonic dilatation without obstruction. She underwent emergency total colectomy with end ileostomy, and histopathology confirmed diffuse ganglioneuromatosis. This case represents one of the oldest reported presentations of megacolon in MEN2B and highlights the importance of recognising gastrointestinal features in all age groups to allow timely surgical intervention and optimise patient outcomes. Categories: General Surgery Keywords: chronic megacolon, ganglioneuromatosis, gi, megacolon, multiple endocrine neoplasia type 2b (men2b), total colectomy Introduction Multiple endocrine neoplasia type 2 (MEN2) is a rare autosomal dominant disorder caused by germline mutations in the RET proto-oncogene. Clinically, it is classified into two phenotypic variants: MEN2A and MEN2B. Extra-endocrine features, including gastrointestinal (GI) manifestations, are more frequent in MEN2B than in MEN2A [1] . In MEN2B, GI symptoms often appear early in life, with constipation and megacolon during infancy or childhood being common non-specific initial signs [2] . These symptoms arise from diffuse ganglioneuromatosis of the bowel wall, which impairs motility and can lead to progressive colonic dilatation [3] . While medical management may provide temporary relief, definitive treatment is usually surgical resection [4] . Although most cases present in early childhood, chronic megacolon can also present much later in life in patients with MEN2B [3] . Case Presentation A 66-year-old woman with MEN2B, diagnosed in childhood, presented with absolute constipation for five days, associated with abdominal distension, nausea, and vomiting. She has been on medical treatment for chronic constipation for many years. She had undergone total thyroidectomy for medullary thyroid carcinoma (MTC) and bilateral adrenalectomy for pheochromocytoma in her youth. On examination, she exhibited marfanoid body habitus, everted eyelids, and prominent lips. The abdomen was grossly distended with audible bowel sounds and diffuse tenderness, but no guarding or rigidity. Laboratory investigations were unremarkable. Computed tomography (CT) abdomen and pelvis showed marked colonic dilatation up to 11.5 cm, with loss of bowel tone, and no evidence of perforation or obstructive lesion (Figures 1-2) . How to cite this article Rana M , Hussain S , Osman S , et al. (December 03 , 2025) Late-Onset Gastroi

FAQs

What is MEN2B and how is it related to gastrointestinal symptoms?

MEN2B is a rare autosomal dominant disorder caused by RET protooncogene mutations. GI symptoms such as constipation and megacolon arise from diffuse ganglioneuromatosis affecting bowel motility.

Why is late-onset megacolon in MEN2B clinically uncommon?

GI manifestations typically appear in infancy or childhood, making presentation in later adulthood rare. This case documents one of the oldest reported presentations of megacolon in MEN2B.

What treatment was performed for the patient’s megacolon?

The patient underwent emergency total colectomy with end ileostomy after imaging showed marked colonic dilatation without obstruction, and histopathology confirmed diffuse ganglioneuromatosis.

Sep 28, 2026

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