Multiple Endocrine Neoplasia Type 1 (MEN1) Presenting as an Invasive Macroprolactinoma Complicated by Acute Bacterial Meningitis

Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant disorder characterized by tumors of parathyroid, anterior pituitary, and pancreatic islet cells. Pituitary adenomas in MEN1 can be aggressive and invade surrounding structures including the skull base. However, acute bacterial meningitis in patients with newly diagnosed macroprolactinomas is an exceptional finding. We present the case of a young man with suppurative meningitis complicating an invasive macroprolactinoma as the initial manifestation of MEN1. A 33-year-old male was admitted to the hospital with fever, headache, and nuchal rigidity and subsequently diagnosed with Haemophilus influenzae bacterial meningitis. Computed tomography (CT) and subsequent magnetic resonance imaging (MRI) of the sella turcica revealed a 5 x 3.5 cm pituitary mass invading both cavernous sinuses and the left sphenoid sinus. Laboratory evaluation was notable for significantly elevated serum prolactin level (2,484 ng/mL, 2.6-13.2) and evidence of hypopituitarism. Primary hyperparathyroidism was indicated by hypercalcemia (13.5 mg/dL, 8.5-10.5), low serum phosphorus (2.0 mg/dL, 2.5-4.9), and elevated intact parathyroid hormone (PTH) level (290 pg/mL, 15-60). No visual field deficits were identified. The patient was managed with hydrocortisone, levothyroxine, and cabergoline. However, cerebral spinal fluid (CSF) rhinorrhea compelled subtotal transsphenoidal resection of the tumor and repair of the CSF leak. Three-and-a-half gland parathyroid resection was performed after recovery from pituitary surgery and successfully treated hypercalcemia. Abdominal MRI revealed a 1.2 cm cystic mass in the neck of the pancreas, and pancreatic polypeptide was approximately fourfold elevated. A clinical diagnosis of MEN1 was made based on the occurrence of macroprolactinoma, multiple parathyroid adenomas, and pancreatic findings. This case appears to be the first in which bacterial meningitis was the initial presentation of an invasive macroprolactinoma in a patient with MEN1.