Multiple endocrine neoplasia with an atypical clinical course and a MEN1 gene variant of uncertain pathogenicity: A...

Multiple endocrine neoplasia type 1 (MEN1) is characterized by the coexistence of multiple endocrine tumors, most commonly due to autosomal dominant mutations in the tumor suppressor gene MEN1. Because this neoplastic disease is rare, diagnosis is often challenging. Some patients remain undiagnosed because of absent or nonspecific symptoms, while others may die before a correct diagnosis is established.

An 88-year-old man presenting with progressive dementia and heat stroke was admitted to our hospital. Close examinations revealed syndrome of inappropriate secretion of antidiuretic hormone and iron deficiency anemia. These conditions were attributable to a pituitary tumor and a duodenal gastrinoma, respectively, which had been identified independently by other physicians more than 6 years earlier. Genetic testing revealed an MEN1 variant of uncertain significance (rs2959656).

As the clinical findings fulfilled the diagnostic criteria, MEN1 was confirmed.

His cognitive decline and behavioral symptoms improved after treatment for syndrome of inappropriate secretion of antidiuretic hormone without dementia-specific medications. Although the pituitary adenoma was initially suspected to be a prolactinoma and treated with cabergoline, insufficient tumor size reduction after 1 year of therapy led to revision of the diagnosis to a nonfunctioning pituitary neuroendocrine tumor.

This case underscores the importance of considering MEN1 even in elderly patients with atypical manifestations, emphasizes the value of integrating prior medical history into diagnosis, and suggests a potential role of rs2959656 in MEN1 pathogenesis.