Lymphocytic hypophysitis masquerading as pituitary adenoma

INTRODUCTION: Pituitary hypophysitis (PH) is characterized by pituitary infiltration of lymphocytes, macrophages, and plasma cells that could lead to loss of pituitary function. Hypophysitis may be autoimmune or secondary to systemic diseases or infections. Based on the histopathological findings PH is classified into lymphocytic, granulomatous, xanthomatous, mixed forms (lymphogranulomatous, xanthogranulomatous), necrotizing and Immunoglobulin- G4 (IgG4) plasmacytic types. OBJECTIVE: To report a case of lymphocytic hypophysitis (LH). CASE REPORT: A 15-year-old girl presented with history of headache, amenorrhea, and history of polyuria for past 4 months. Initial evaluation had suppressed follicular stimulating hormone (<0.01 mIU/ml), high prolactin levels (110.85 ng/ml) and diabetes insipidus (DI). Magnetic resonance imaging of sella was suggestive of pituitary macroadenoma with partial compression over optic chiasma. Patient underwent surgical decompression. Yellowish firm tissue was evacuated and xanthochromic fluid was aspirated. Histopathology was suggestive of LH. She resumed her cycles postoperatively after 4 months, prolactin levels normalized, however, she continues to have DI and is on desmopressin spray. This case has been presented here for its rare presentation in an adolescent girl because it is mostly seen in young females and postpartum period and its unique presentation as an expanding pituitary mass with optic chiasma compression. CONCLUSION: Definitive diagnosis of LH is based on histopathological evaluation. Therapeutic approach should be based on the grade of suspicion and clinical manifestations of LH.