SUN-056 - Atypical Presentation of Igg4-Related Hypophysitis Causing Central Adrenal Insufficiency

Background:
IgG4-related disease (IgG4-RD) is a progressive, immune-mediated condition characterized by IgG4-secreting plasma cell infiltration of tissues. While autoimmune pancreatitis and retroperitoneal fibrosis are classic manifestations, pituitary involvement is rare, with a prevalence of approximately 3% in patients with IgG4-RD. We describe a patient with IgG4-RD presenting with atypical, clinically asymptomatic IgG4-related hypophysitis and central adrenal insufficiency (AI).
Clinical

Case:
A 55-year-old woman with hypertension, hyperlipidemia, and prior ischemic stroke presented with epigastric pain. Labs showed sodium of 123 mEq/L (135–145 mEq/L), AST 272 U/L (8-48 U/L), ALT 292 U/L (7-55 U/L), and alkaline phosphatase 298 U/L (40-129 U/L). Abdominal ultrasound showed cholelithiasis and a dilated common bile duct measuring 1.4 cm. The patient underwent MRCP, which revealed a diffuse infiltrative process involving the pancreas. Endoscopic ultrasound-guided pancreatic biopsy revealed lymphoplasmacytic sclerosing pancreatitis, with immunohistochemistry positive for IgG4. Evaluation of hyponatremia revealed morning cortisol 2.6 µg/dL (10-20 µg/dL), TSH 0.87 µIU/mL (0.4-4 µIU/mL), and free T4 0.54 ng/dL (0.8–1.8 ng/dL), consistent with central AI and hypothyroidism. CT head showed an 8-mm suprasellar lesion. Pituitary MRI demonstrated a 9-mm enhancing infundibular mass with loss of the posterior pituitary bright spot, consistent with hypophysitis. Serologic testing showed IgG 4,851 mg/dL (600–1600 mg/dL) and IgG4 2,229 mg/dL (2-96 mg/dL). The patient was diagnosed with IgG4-related hypophysitis with partial hypopituitarism and autoimmune pancreatitis. Hydrocortisone and levothyroxine were initiated. Patient’s IgG and IgG4 levels were monitored and HPA axis was reassessed outpatient.

Conclusion:
IgG4-RD should be considered in patients with unexplained hypophysitis as well as in the evaluation of patients with central AI, particularly in the setting of systemic inflammatory disease. A high index of suspicion and prompt recognition is therefore critical, given the high responsiveness of IgG4-RD to glucocorticoid therapy when treated early. Likewise, in patients with IgG4-RD, it may be worthwhile to screen for AI or hypophysitis. Our patient had no symptoms of AI apart from hyponatremia, and her hypophysitis likewise presented without visual symptoms or headache. Treatment for the IgG4-RD with steroids would have masked the HPA axis suppression.

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