Multiple endocrine neoplasia, type 2b, as a cause of megacolon.

A case of multiple endocrine neoplasia, type 2b, is reported presenting with weight loss, neck masses, and constipation. A medullary thyroid carcinoma was found to be present together with a megacolon. In this syndrome, the diagnosis of the thyroid tumor is rarely made before it is well established; hence an appreciation of the accompanying gastrointestinal symptoms and signs may lead to early diagnosis. The case had many classical features, such as ganglioneuromata involving the tongue, lips, and eyelids and typical biochemical findings. However, several unusual findings were present, such as the absence of any skeletal abnormalities, an acute onset of constipation, and the presence of bony metastases and the case is reported to illustrate the complexity of this uncommon entity.