ODP648 MEN1 vs MEN4: when we cannot find a mutation

Abstract MEN1 is an autosomal dominant syndrome characterized by involvement of several endocrine and non-endocrine organs. The most common organs that are affected include pituitary, parathyroid, and/or pancreas. In 10-30% patients, no germline mutations in the menin gene identified, presenting a diagnostic challenge. This case raises question possible MEN4 syndrome, which shares similar phenotype to MEN 1 with mutation CDKN1B. Clinical 59 y/o female PMH HTN, obesity, hypothyroidism initially presented our clinic 2018 for evaluation hypercalcemia. She prior was seen 2005 prolactinoma outside endocrinologist but lost follow up. Per history, she had pituitary MRI 1991 work up amenorrhea found have prolactinoma. placed on bromocriptine at time; after repeat prolactin levels were be normal, discontinued 2019 then restarted few months later due uptrending level. During visit us, her hypercalcemia included calcium 11. 0 mg/dL PTH level 93 pg/mL normal albumin, vitamin D, renal function. Patient negative sestamibi scan 10 mm×5 mm×12 mm enhancing nodule along left thyroid gland lateral margin esophagus, suggesting parathyroid adenoma. subsequently underwent successful inferior parathyroidectomy July normalization levels. No other enlarged. Given adenoma, sent genetic testing; evaluated 7 variants all including MEN1, CDKN1B, GNA11, AP2S1, CASR, CDC73, RET. Of note, has family history or any tumors. However, further testing still performed evaluate pancreatic neuroendocrine tumor CT abdomen, gastrin, C peptide, chromogranin-A, glucagon, VIP, 5-HIAA. Her initial came back abdomen 2020. recently lab results 2021 revealed elevated gastrin 124 chromogranin A 262 ng/mL (<=93), diagnosis gastrinoma confirmed PPIs started. Discussion highlights importance continued surveillance patients multiple organ neoplasia despite it also supports likelihood unidentified given improbable chance this patient 3 independent Possibilities missed phenocopies. likely upstream not identified could represent either vs Presentation: date time listed