7480 Isolated IgG4-Related Infundibulo-Hypophysitis

Abstract Disclosure: M. Allen: None. R.T. Beck: None. N.T. Zwagerman: None. R.J. Ryzka: None. D. Coss: None. A. Fisco: None. A.G. Ioachimescu: None. Background: 130 cases of IgG4-related hypophysitis (IgG4-RH) have been reported, usually in context of multi-organ IgG4-disease (e.g., siladenitis, pancreatitis, retroperitoneal fibrosis). Among patients with IgG4-disease, up to 5% develop hypophysitis. Presentation entails mass effects, AVP-D and anterior hypopituitarism.Case report: A 72-year-old man with history of hyperlipidemia presented with gradual decrease in strength, energy, appetite, libido, and depressed moods. Laboratory tests (8 AM) indicated undetectable AM cortisol, ACTH 6.8 pg/mL (7.2-63.3), TSH 0.20 mIU/mL (0.35-4.94), free thyroxine 0.64 ng/dL (0.7—1.48), prolactin 50.9 ng/mL (3.46-19.4), IGF-1 57 ng/mL (53-222), testosterone 7 ng/dL (240-950), LH 0.16 mIU/mL (0.57-12.07), and FSH 1.5 mIU/mL (1.0-12). MRI revealed a homogenously enhancing nodular suprasellar mass adjacent to the hypothalamus (0.8x0.7x0.8 cm) and contiguous with a 0.5 cm area of infundibular thickening. Neuro-ophthalmological evaluation was normal. In absence of mass effects, patient was monitored conservatively and treated with hydrocortisone, levothyroxine and testosterone replacement. Six months later, the mass enlarged to 1.2x0.8x1.1 cm. Patient underwent a transsphenoidal biopsy which revealed a dense fibrous mass with lymphoplasmacytic infiltration. Most cells stained for CD138 and IgG4. Postoperatively, serum IgG and complement levels, inflammatory markers, hemogram, serum protein electrophoresis, amylase and lipase were normal. CT chest and abdomen and thyroid ultrasound were unremarkable. After 4 weeks of prednisone 40 mg daily, the nodular lesion significantly decreased on MRI (0.6x0.5x0.4 cm). Prednisone was gradually tapered to 5 mg daily over 3 months. After 2 months of physiologic prednisone therapy, imaging remained stable. During follow-up of 1.5 years, no systemic IgG-4 disease was apparent and patient remained on glucocorticoid, thyroid and testosterone replacement.Discussion: Suprasellar masses can be inflammatory, infiltrative, infectious or neoplastic. The possibility of IgG4-RH should be considered even in absence of IgG4 systemic disease, as it happened in our case. Primary involvement of the infundibulo-hypophysis was suggested by a retrospective review study that found isolated IgG4-RH in 41% specimens initially diagnosed as primary autoimmune hypophysitis. Our case maintained a good radiological response after prednisone taper to physiologic doses. Response to prednisone is generally good in IgG4-RH, but relapse can occur upon taper, and long-term studies are lacking. Conclusion: We present a histologically-confirmed case of isolated IgG4-RH presenting with clinical manifestations of anterior hypopituitarism. Diagnosis and management of IgG4-RH requires multidisciplinary collaboration (endocrinology, rheumatology, neurosurgery, neuropathology and neuroradiology). Presentation: 6/3/2024