[A rare case of Rosai-Dorfman disease involving the pituitary stalk and presenting initially with diabetes insipidus].

Rosai-Dorfman disease (RDD) is a rare form of non-Langerhans cell histiocytosis. In August 2024, a 38-year-old man was admitted to the Department of Endocrinology, The Third Xiangya Hospital of Central South University. He initially presented with diabetes insipidus, and his condition gradually progressed over a 15-year disease course, eventually leading to panhypopituitarism. Imaging examinations revealed marked thickening of the pituitary stalk, 2 meningioma-like dural nodules, multiple osteolytic lesions, mild interstitial pneumonia, and urinary system involvement. RDD was confirmed by a pituitary stalk biopsy, and a BRAF V600E mutation was identified. The patient subsequently received targeted therapy with the BRAF inhibitor dabrafenib in combination with pituitary hormone replacement therapy. Follow-up brain magnetic resonance imaging after 8 months of treatment demonstrated a reduction in pituitary stalk thickening and complete disappearance of the 2 meningioma-like dural nodules. The patient's quality of life also improved substantially. This retrospective analysis of the case may assist clinicians in determining the etiology and differential diagnosis of pituitary stalk thickening and enhance awareness of RDD as a rare disease.