SUN-273 A Rare Case of IgG4-Related Hypophysitis

Introduction: Hypophysitis is an acute or chronic inflammation of the pituitary gland and is an important diagnostic consideration in a patient with a sellar lesion. The annual incidence of hypophysitis is estimated to be 1 in 7–9 million and it accounts for approximately 0.4% of pituitary surgery cases. The following highlights a rare case of isolated IgG4-related hypophysitis Clinical Case: A 63-year-old Caucasian female presented with sudden onset of diplopia and decreased visual acuity. This was associated with a 3-month history of headaches and 5-lbs weight loss. Past medical history was significant for hypertension and a 1.5cm sellar/suprasellar mass incidentally discovered during the work-up for persistent headaches 1-month prior. Initial anterior pituitary hormone evaluation was normal and the patient was scheduled for endoscopic endonasal resection of a presumed non-functioning pituitary adenoma. Family history was negative for pituitary tumors or hyperparathyroidism. Physical examination was notable for medial deviation of her left eye but neurologic examination was otherwise normal. Laboratory studies were notable for a normal TSH [1.769 uIu/ml (normal: 0.3–5.0)] and low free T4 [0.44 ng/ml (normal: 0.89–1.78)] consistent with central hypothyroidism; an inappropriately normal FSH for a postmenopausal woman [5.6 mIu/ml (normal: 0.3–10.5), and a normal prolactin level [16 ng/ml (0.6–20)]. An 8am cortisol was low at 2mcg/dL (5–21) with an ACTH level of 10 pg/mL (9–46). IGF-1 was normal at 89 ng/mL (41–279). Repeat pituitary MRI imaging demonstrated a homogenously enhancing sellar/suprasellar mass measuring 3.8 cm with displacement of the optic chiasm. Serum IgG4 levels were normal. The patient was started on 50mg IV hydrocortisone every 8 hours for central adrenal insufficiency and levothyroxine 88 mcg daily for central hypothyroidism and underwent an endoscopic endonasal biopsy of the lesion. Surgical pathology was notable for plasma cell-rich lymphohistiocytic hypophysitis and IgG4 plasma cells constituted >40% of the total plasma cell population. The patient subsequently received 1g of rituximab and repeat imaging one week later showed marked improvement in the size and extent of the lesion. The patient was discharged on prednisone and levothyroxine and received a second dose of rituximab at follow-up. The patient reports a decrease in the frequency of her headaches but continues to endorse diplopia. Conclusion: IgG4-related hypophysitis typically presents as part of a multifocal systemic process. This case highlights a rare entity of IgG4-related hypophysitis without other features of systemic disease and with normal serum levels of IgG4. Although glucocorticoids are universally regarded as the first line of therapy, an immunosuppressive agent or B-cell depletion therapy such as Rituximab may improve remission and decrease the risk of relapse.