Idiopathic Granulomatous Hypophysitis Presenting as Pituitary Apoplexy: A Rare Manifestation of a Rare Disorder

Introduction: Idiopathic granulomatous hypophysitis (IGH) is a chronic inflammatory lesion of the pituitary gland. It occurs rarely—only 23 cases have been reported in the literature—and it typically presents with chronic onset of headache and slow development of visual deficits. It is diagnosed only on pathologic examination. IGH has never been reported to present as pituitary tumor apoplexy. We report possibly the first case of IGH manifesting as pituitary apoplexy in a young woman, who was diagnosed preoperatively on MR imaging as harboring a pituitary macroadenoma.

Methods: A 36-year-old woman presented with the sudden onset of left-sided retro-orbital headaches, diplopia, and left ptosis, and she admitted to recent menstrual irregularities with intermittent galactorrhea. MR imaging of the brain demonstrated an intensely enhancing 1.9 × 1.1 × 1.3 cm enhancing sellar mass lesion with suprasellar extension, mass effect on the left cavernous sinus, and an area of low signal on T2-weighted imaging, consistent with recent hemorrhage. Pituitary tumor apoplexy was suspected, and the patient underwent an emergent transsphenoidal removal of the tumor to decompress the optic nerves and the left cavernous sinus.

Results: Microscopic examination demonstrated chronic granulomatous inflammation with extensive caseous necrosis. Palisading of epithelioid cells around the zones of necrosis was noted, as well as multinucleated giant cells within the necrotic zones. Postoperatively, the patient's ophthalmoplegia resolved completely; visual fields and acuity were normal. An extensive systemic workup for sarcoidosis, tertiary syphilis, and Wegener's granulomatosis was carried out; all results were negative. A diagnosis of IGH was established based on histopathologic findings and lack of systemic granulomatous pathology. Postoperative imaging 18 months out demonstrated excellent resolution of the mass lesion with decompression of the optic chiasm and cavernous sinus.

Conclusion: To our knowledge, idiopathic granulomatous hypophysitis has never before been reported to present as pituitary apoplexy. As it can appear identical to pituitary adenoma, both radiographically and clinically, a high index of suspicion is warranted. Treatment consists of operative intervention in the face of acute neurological deterioration and evidence of mass effect, with hormone replacement therapy commonly required for hypopituitarism either pre- or postoperatively. In the presence of caseous necrotizing granulomas, a thorough workup for tuberculosis, sarcoidosis, and other granulomatous etiologies is warranted.