Endocrine Abstracts

Multiple endocrine neoplasia (MEN) includes a group of autosomal dominant disorders, associated with the development of a variety of endocrine and non-endocrine manifestations. MEN4 is a rare and the latest reported type in the spectrum of the MEN syndromes. MEN4 was discovered initially in rats (MENX) and later in humans. It is caused by germline and somatic mutations in the cyclin-dependent kinase inhibitor 1B (CDKN1B) tumor suppressor gene, which encodes nuclear protein p27 (IFI27), a key regulator of cell cycle progression. The most common phenotype of MEN4 is primary hyperparathyroidism (PHPT), followed by pituitary adenomas and rarely NETs. MEN4 and MEN1 syndromes have similar phenotypes. However, in MEN4 the disease manifestations appear later in life, associated with an improved life- expectancy and a different prevalence. We present an adult woman with MEN4 who presented with a non-functioning pituitary adenoma, an adrenocortical adenoma causing mild Cushing syndrome, a parathyroid adenoma associated with mild PHPT and benign intestinal polyps. We identified that she is harboring a novel heterozygous CDKN1B gene pathogenic variant, p.Lys96GInfsTer 29.