2026 Poster Presentations
P274: IGG4-RELATED HYPOPHYSITIS MASQUERADING AS A PITUITARY MACROADENOMA: A CASE REPORT
Maxwell A Marino1; Ali Jamshidi, MD2; 1Riverside University Health System; 2Kaiser Permanente Woodland Hills Medical Center
Background: IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition that rarely affects the pituitary. When it does, it may mimic a pituitary macroadenoma and is termed IgG4-related hypophysitis (IgG4-RH). Fewer than 100 cases have been reported, and diagnosis is often delayed due to radiologic similarity to neoplasms. We present a rare case of isolated IgG4-RH with coexisting Rathke’s cleft cyst.
Methods: A 44-year-old male presented with progressive bitemporal hemianopsia and fatigue. MRI showed a 14 × 15 × 20 mm enhancing sellar/suprasellar lesion compressing the optic chiasm. The working diagnosis was pituitary macroadenoma. He underwent endoscopic endonasal transsphenoidal resection with intraoperative stereotactic navigation. Histopathology was reviewed for definitive diagnosis.
Results: Surgical resection achieved decompression of the optic chiasm. Pathology revealed dense lymphoplasmacytic infiltrates, storiform fibrosis, and more than 40% IgG4-positive plasma cells per high-power field. No adenoma or malignancy was identified. Coexisting Rathke’s cleft cyst was also present. The patient recovered without neurological complications and was discharged on postoperative day two. Follow-up imaging showed expected postsurgical changes. He was referred for systemic evaluation to assess for broader IgG4-related disease.
Conclusion: IgG4-related hypophysitis is a rare but important mimic of pituitary macroadenoma. Surgical decompression offers tissue diagnosis and symptom relief. This case emphasizes the need to consider IgG4-RD in the differential for sellar masses. Identification of IgG4-RH prompts systemic workup and can guide long-term immunosuppressive therapy if indicated. Skull base surgeons should remain aware of this entity, particularly in cases with atypical imaging or pathology findings.