Endocrine Abstracts

JOINT2278

Multiple Endocrine Neoplasia type 2B (MEN2B) is a rare autosomal dominant disease caused by mutations in the RET proto-oncogene. It is associated with medullary thyroid cancer (MTC) and pheochromocytoma, along with systemic manifestations, including marfanoid habitus, mucosal neuromas, and gastrointestinal ganglioneuromatosis. We present a case of a 33-year-old man with uncontrolled hypertension, sinus tachycardia, hyperhidrosis, and marfanoid habitus. He was diagnosed with bilateral pheochromocytoma and subsequently MTC. Genetic testing confirmed a heterozygous RET mutation (pMet918Thr, exon 16), consistent with MEN2B. He underwent bilateral adrenalectomy, with pathology confirming benign pheochromocytomas. Later that year, he had surgery for MTC with lymph node metastases (total thyroidectomy with bilateral central and lateral neck lymph node dissection). Despite treatment, he remains with persistent disease, with a calcitonin doubling time of 36 months. He is now under replacement therapy with hydrocortisone (20+10 mg/day), fludrocortisone (0.1 mg/day), and levothyroxine (125 mg/day). The patient exhibits marfanoid features, including tall stature, pectus excavatum, arachnodactyly, and scoliosis. Additionally, he presents mucosal neuromas of the tongue and lips. Ocular complications have arisen due to absent tear production, leading to severe corneal ulceration. His gastrointestinal history includes intestinal ganglioneuromatosis, with surgeries at the age of 9 and 30 for bowel obstruction and perforated diverticulitis with peritonitis, respectively. He also has valvular heart disease, manifesting as mitral and tricuspid valve prolapse. Of particular interest is the onset of type 1 diabetes at the age of 34, one year after the MEN2B diagnosis. He is managed with multiple daily insulin injections (degludec and aspart), but his glycemic control remains suboptimal (HbA1c 10%). While secondary diabetes is common in patients with pheochromocytoma due to excessive catecholamine secretion, the coexistence of type 1 diabetes in MEN2B is extremely rare, with very few cases documented in the literature. This case illustrates the complexity of MEN2B, with its combination of neuroendocrine tumors and extensive multisystemic involvement. The unique coexistence of type 1 diabetes adds complexity to the patient’s care, highlighting the need for ongoing research to explore any potential connections between MEN2B and autoimmune dysregulation. Multidisciplinary care is essential for managing the diverse complications of this rare syndrome.