Central Nervous System Blastomycosis Presenting as Hypophysitis Mimicking Neurosarcoidosis: A Case Report

Abstract

Abstract: Central nervous system (CNS) blastomycosis manifesting as hypophysitis is an exceptionally rare fungal presentation that can mimic other sellar masses, posing significant diagnostic challenges in immunocompetent individuals. A woman in her early 20s with atopic dermatitis previously on dupilumab presented with headaches, diplopia, and blurred vision, with magnetic resonance imaging (MRI) revealing a sellar/suprasellar mass. Initial surgical pathology demonstrated granulomatous inflammation, which led to empirical treatment with corticosteroids and infliximab for presumed neurosarcoidosis. Following progressive neurologic decline, central diabetes insipidus, and cerebral infarcts, cerebrospinal fluid (CSF) cultures grew Blastomyces dermatitidis six weeks into her hospitalization. The patient was treated with one month of liposomal amphotericin B followed by a year and three months of voriconazole, resulting in substantial resolution of her neurologic and endocrine symptoms, normalization of CSF pleocytosis, and clearance of urine antigens. Ultimately, blastomycosis-associated hypophysitis must be considered in the differential diagnosis of sellar lesions, particularly in patients from endemic regions like Illinois. Furthermore, clinicians must recognize that empirical corticosteroid and infliximab therapy may contribute to rapid progression of an unrecognized fungal infection. This case underscores the necessity of maintaining a broad differential and pursuing prolonged diagnostic evaluation to avoid dangerous misdiagnoses, enable timely targeted antifungal therapy, and prevent permanent complications.