Delayed diagnosis of MEN1 after kidney transplantation: unrecognized pre-transplant features and implications for clinical practice.

Multiple endocrine neoplasia type 1 (MEN1), characterized by multiglandular endocrine tumors such as hyperparathyroidism (HPT), is an autosomal dominant disorder caused by mutations of the MEN1 gene. In patients with chronic kidney disease (CKD), abnormalities in calcium-phosphate metabolism may obscure this diagnosis, making the recognition of MEN1 challenging. A 68-year-old man with end-stage renal disease underwent an ABO-compatible living-donor kidney transplantation (KT); however, persistent hypercalcemia prompted further evaluation, which revealed recurrent HPT with bilateral parathyroid enlargement. Pre-transplant imaging revealed an adrenal adenoma and a pancreatic tail lesion. Subsequent pituitary magnetic resonance imaging and genetic testing confirmed the diagnosis of MEN1. A retrospective review of the patient's medical history revealed several pre-transplant findings suggestive of MEN1 that had not been recognized. This case highlights that MEN1 may remain unrecognized in KT candidates owing to the occurrence of metabolic abnormalities also associated with CKD. The early recognition of MEN1 in KT candidates with recurrent or multiglandular hyperparathyroidism may improve pre-transplant risk assessment and enable appropriate long-term oncological surveillance.