Novel Germline p.Gly42Val MEN1 Mutation in a Family with Multiple Endocrine Neoplasia Type 1 - Excellent Response of Prolactinoma to Cabergoline.

We report on a 27-year-old male patient presenting with renal colic secondary to hyperparathyroidism. Further investigations confirmed a diagnosis of type 1 multiple endocrine neoplasia and revealed a 2.0 cm pancreatic neuroendocrine tumour as well as a pituitary macroadenoma with significantly elevated prolactin levels. The patient underwent three-gland parathyroidectomy, a left pancreatectomy, and received dopamine agonist treatment. Genetic testing revealed a novel germline heterozygote missense mutation in the MEN1 gene (p.Gly42Val) which affects the Smad3 binding domain of the MENIN protein. The same mutation was found in the patient's mother, who on further testing was found to have hyperparathyroidism, a pituitary microadenoma and bilateral adrenal hyperplasia without pituitary or adrenal hormone excess. This case report raises the importance of genetic testing for MEN1 syndrome in a patient even when family history appears to be negative. Following genetic counselling, genetic cascade screening should be considered in family members to identify further gene carriers.