MON-096 Swollen Painful Orbit and Brain Lesion as Presenting Symptoms in IgG4-related Hypophysitis Resulting in Central Diabetes

Abstract S. Alshami: None. S. Devarapalli: None. A. Kasireddy: None. A. Albashaireh: None. J. Henske: None. Introduction: IgG4-related disease (IgG4-RD) is an immune-mediated condition characterized by lymphoplasmacytic infiltration, fibrosis, elevated serum IgG4 level, and IgG4+ cells in the affected tissues. It most frequently involves the pancreato-biliary tract, retroperitoneum/aorta, head and neck, and salivary glands. If left untreated, it can lead to permanent organ injury and death, therefore early diagnosis and management is crucial. Case: A 54-year-old female presented with worsening left orbital swelling and pain. Her symptoms began with headaches, and she was diagnosed with cluster headaches. Three weeks prior, she reported polydipsia, polyuria, and nocturia. CT brain showed a left superior ophthalmic vein thrombosis, periorbital edema, and a 6 mm right frontal ring enhancing lesion concerning for occult neoplasm versus infectious process. Antibiotics were started. CSF was positive for HSV-1 meningitis and she was treated with acyclovir. To rule out malignancy, a CT chest/abdomen/pelvis was done which revealed multiple lung nodules. Repeat brain imaging showed no improvement of cerebral lesions. Antifungals were started. Repeat brain MRI showed no significant changes from initial imaging. Subsequently, she underwent endoscopic transsphenoidal biopsy of the parasellar inflammatory tissue which returned consistent with a chronic inflammatory process with features suggestive of IgG4-RD of the orbit and CNS. Prednisone was started and vision rapidly returned to baseline. Polyuria, polydipsia, and nocturia persisted. Urine osmolality was low at 56 mOsm/kg. Serum sodium was normal as she was able to drink to thirst. Trial of desmopressin 0.5 mcg subcutaneously daily resulted in significant improvement in her symptoms. A diagnosis of diabetes insipidus secondary to IgG4-related hypophysitis was established, and she was discharged on oral desmopressin 100 mcg daily. Discussion: We present a unique case of IgG4-RD involving the posterior pituitary resulting in central diabetes insipidus. The key learning point is that when there is clinical concern for diabetes insipidus in the absence of an intracranial tumor, one should further investigate the etiology including vascular (infarction or hemorrhage), infectious (meningitis, encephalitis, or tuberculosis), granulomatous (e.g. sarcoidosis), or autoimmune/inflammatory causes (including IgG4-RD, lymphocytic, and xanthogranulomatous hypophysitis). Early diagnosis and treatment are crucial in managing IgG4-related disease to avoid long-term complications. Monday, June 3, 2024