Context
The acute presentation of Immunoglobulin G4 (IgG4)-related hypophysitis can be indistinguishable from other forms of acute hypophysitis and histology remains the diagnostic gold standard. The high recurrence rate necessitates long term immunosuppressive therapy. Rituximab (RTX) has been shown to be effective in systemic IgG4-related disease (IgG4-RD), but experience with isolated pituitary involvement remains limited.

Case description
We report three female patients with MRI findings suggestive of hypophysitis. All patients underwent transsphenoidal biopsy and fulfilled diagnostic criteria for IgG4-related hypophysitis. Treatment with GCs (GC) resulted in good therapeutic response in patients 1 and 2, but the disease recurred on tapering doses of GCs. GC treatment led to emotional lability in Patient 3 necessitating dose reduction. All three patients received RTX and Patients 2 and 3 received further courses when symptoms returned and B-cells repopulated. Patient 3 did not receive RTX until 12 months from onset of symptoms. Patient 1 was not able to have further RTX treatments due to an allergic reaction when receiving the second dose. RTX treatment resulted in sustained remission and full recovery of anterior pituitary function in Patients 1 and 2 with complete resolution of pituitary enlargement. By contrast, Patient 3 only showed symptomatic response following RTX treatment, but pituitary enlargement and hypofunction persisted.

Conclusion
RTX treatment for IgG4-related hypophysitis resulted in sustained remission in two patients treated early in the disease process, but only achieved partial response in a patient with chronic disease suggesting that early therapeutic intervention may be crucial to avoid irreversible changes.