Megacolon Associated with Multiple Endocrine Neoplasia Type 2B: A Case Successfully Managed with Ileostomy

Multiple endocrine neoplasia type 2B (MEN2B) is a rare genetic disorder characterized by medullary thyroid carcinoma, pheochromocytoma, mucosal neuromas, and Marfanoid body habitus. Megacolon is a common non-endocrine manifestation, with approximately 75% of patients experiencing gastrointestinal symptoms, such as constipation or diarrhea, often as early clinical signs. Although these symptoms may be important diagnostic signs, there are currently no distinct therapeutic guidelines. Here, we report a case of MEN2B-associated megacolon that was managed surgically, resulting in a favorable outcome.

A 23-year-old man with a history of chronic constipation was diagnosed with MEN2B at 14 years of age based on findings of medullary thyroid carcinoma, mucosal neuromas, and rectal biopsy-confirmed intestinal ganglioneuromatosis. He previously underwent total thyroidectomy and emergency transverse colectomy for volvulus. Progressive colonic dilatation led to abdominal distension and organ compression, prompting referral. Imaging confirmed marked colonic dilation. Laparoscopic subtotal colectomy with ileosigmoid anastomosis was performed. Postoperatively, the patient experienced recurrent ileus and required hospital readmission for small bowel obstruction. Two months postoperatively, the patient presented with a gastrointestinal perforation at the anastomotic site and underwent resection with terminal ileostomy. The postoperative course was uneventful, and the patient remained symptom-free.

MEN2B-associated megacolon results from diffuse intestinal ganglioneuromatosis. Considering its progressive and extensive nature, decompression via stoma creation may be necessary to improve the postoperative outcomes and reduce the risk of symptom recurrence. Increased awareness and individualized surgical planning are crucial for treating this rare but serious complication of MEN2B.