IgG4-negative pituitary inflammatory pseudotumor with sphenoidal involvement resembling a macroadenoma.

Background: Inflammatory pseudotumors (IPTs) are rare benign conditions of unknown etiology that can affect any part of the body. IPTs are most commonly associated with Immunoglobulin G4 (IgG4)-related disease. Central nervous system IPTs, especially with pituitary involvement, are even rarer entities. The presence of an IgG4-negative pituitary IPT with simultaneous extracranial involvement has not been reported.

Case Report: We present the case of a 41-year-old female with past medical history of rheumatoid arthritis and a diagnosis of pituitary IPT with coexisting sphenoidal (extracranial) involvement mimicking a pituitary macroadenoma at presentation. The patient underwent multiple consecutive biopsies, and an extensive workup prior to establishing the diagnosis. Laboratory work-up showed normal serum IgG4 and unremarkable liver function tests.

Conclusion: Pituitary lesions with simultaneous sphenoidal involvement in patients with IgG4-negative systemic inflammatory disease should raise the clinical suspicion for intracranial IPTs, as these tumors can mimic aggressive counterparts causing adjacent bony erosion, and local invasion.