SAT-091 - Hypothalamic Hemorrhage and Bilateral Facial Palsy in Diffuse Large B‑Cell Lymphoma Masquerading as Autoimmune Hypophysitis

Background: Secondary CNS involvement occurs in ~5% of diffuse large B-cell lymphoma (DLBCL) patients (1), yet hypothalamic infiltration with bilateral cranial nerve VII palsy and multifocal extranodal disease as the presenting diagnostic challenge is exceptionally uncommon. CNS lymphoma often mimics autoimmune hypophysitis clinically and radiographically.

Case: An 80-year-old woman with JAK2-positive polycythemia vera developed progressive bilateral facial paralysis (House-Brackmann VI), dysphagia, and hypothalamic hemorrhage. Initial workup showed a 1.2 cm enhancing hypothalamic mass with stalk thickening, hyperprolactinemia (133.2 ng/mL), suppressed gonadotropins (FSH 3.6, LH < 0.1), and positive ANA (1:320), suggesting autoimmune hypophysitis. However, imaging revealed multifocal involvement: bilateral CN VII enhancement, right pterygoid muscle infiltration with CN V3 enhancement, and extensive extranodal disease on PET-CT (bilateral adnexal masses, lymphadenopathy, left thigh lesions with necrosis). CSF flow cytometry was negative; right inguinal node biopsy confirmed CD10-positive DLBCL. She developed panhypopituitarism with adrenal insufficiency (cortisol 24.1→11.8 μg/dL; ACTH 1.5 pg/mL) requiring hydrocortisone. Mini R-CHOP and high-dose methotrexate normalized prolactin (6.9 ng/mL), confirming stalk effect, but facial palsy and dysphagia persisted, necessitating permanent tube feeds. Complications included rituximab infusion reaction requiring ICU care, COVID-19/influenza A coinfection, upper extremity DVT, and severe malnutrition. Endocrine management required stress-dose protocols, levothyroxine escalation (50→125 mcg), and emergency injectable hydrocortisone provision.

Conclusion: This case illustrates diagnostic complexity when CNS DLBCL mimics autoimmune hypophysitis. Hypothalamic lymphoma with bilateral cranial nerve involvement requires tissue diagnosis to exclude autoimmune etiologies. PET-CT, histologic confirmation, and high suspicion for malignancy in atypical pituitary-hypothalamic masses are critical. Permanent endocrinopathies, particularly adrenal insufficiency, necessitate lifelong management and adrenal crisis education.

(1) Bobillo S, et al. Haematologica. 2023;108(3):673-689. doi:10.3324/haematol.2022.281457.

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