A Rare Case of Acromegaly and Prolactinoma in MEN4 Caused by a CDKN1B Mutation.

Background/Objective: Multiple endocrine neoplasia (MEN) comprises a group of rare autosomal dominant genetic disorders characterized by the development of benign or malignant tumors in 2 or more endocrine glands, most commonly including the thyroid, parathyroid, pituitary, adrenal glands, and pancreatic neuroendocrine tissues. MEN4 is a recently recognized subtype that phenotypically overlaps with MEN1 and is caused by germline mutations in the cyclin-dependent kinase inhibitor 1B (CDKN1B) gene. However, due to the limited number of reported cases and the lack of standardized clinical guidelines, the clinical characteristics of MEN4 remain insufficiently understood. Case report: A 59-year-old female presented to our department with progressive facial changes for over 8 years and a pituitary mass detected 6 months prior. Whole-exome sequencing identified pathogenic mutations in the CDKN1B gene, confirming the diagnosis of MEN4. Conclusion: We report a rare case of MEN4 presenting with acromegaly, hyperparathyroidism, and papillary thyroid cancer, caused by a CDKN1B mutation. This case highlights the phenotypic diversity of MEN4 and underscores the importance of genetic testing in patients with overlapping endocrine neoplasms. We also added a literature review to raise clinical awareness of MEN 4 and improve management.