Erdheim-Chester Disease Presenting as a Suprasellar Mass.

Erdheim-Chester disease (ECD) is a rare, sporadic, non-Langerhans cell histiocytosis with multiorgan involvement. Less than half of patients present with central nervous system (CNS) involvement, usually affecting the hypothalamic-pituitary axis (HPA), meninges, and brain parenchyma. CNS-only involvement is extremely rare and can lead to challenges in both diagnosis and management. Clinical course of the disease is varied, ranging from indolent to disabling and life-threatening forms. We report a case of a 55-year-old woman who presented with panhypopituitarism and central diabetes insipidus (DI) in 2016 and was found to have a rapidly enlarging suprasellar mass with non-specific radiologic features. Transcortical biopsy at the time of presentation was inconclusive, and high-dose corticosteroid therapy with close clinical follow-up was initiated. Over a period of six months, the patient had progressive disease with involvement of the hypothalamus and profound tracking cytotoxic edema. Surgical management in the form of endonasal, extended transsphenoidal resection was performed. Final pathology demonstrated a histiocytic neoplasm positive for BRAF V600E mutation (VE1) by immunohistochemistry, consistent with ECD. This case highlights the diagnostic challenges associated with ECD involving the CNS, particularly in anatomically complex regions where tissue sampling may be limited and histologic findings non-specific. While BRAF-targeted therapies were not routinely available at the time of the patient's presentation, identification of BRAF mutations has significant therapeutic implications, enabling the use of targeted therapies in patients with unresectable or progressive disease. This case underscores the importance of maintaining a high index of suspicion in patients presenting with central DI with indeterminate suprasellar lesions.