E-Poster Presentation ESA-SRB-ANZBMS 2021

Case: A 68-year-old male presented with 6 months of decreasing libido, erectile dysfunction and increase lethargy. Pituitary panel revealed hypogonadotropic hypogonadism with FSH 2.3 IU/L, LH 1.7 IU/L, testosterone 1.2 nmol/L. MRI pituitary showed an abnormally thickened and enhanced pituitary stalk and posterior pituitary measuring 1cm x 0.6cm and extending up to the hypothalamus. Pan CT  revealed mild mediastinal lymphadenopathy. Mediastinoscopy and lung biopsy demonstrated minor chronic inflammatory changes consistent with chronic bronchitis without evidence of malignancy or granulomatous disease. Subsequent PET scan was negative for any abnormal uptake.

Trial of prednisolone 25mg for 3 months resulted in radiological improvement however treatment was ceased due to insomnia. Several weeks later diabetes insipidus and hypothyroidism developed requiring desmopressin and thyroxine replacement.

Pituitary stalk biopsy demonstrated significant fibrous tissue with mixed chronic inflammatory cell infiltrate, that was predominately lymphocytic with a moderate number of IgG4+ plasma cells on immunohistological staining. Serum IgG4 was elevated at 3.32 g/L [reference range 0.030-2.010 g/L]. Hence, a diagnosis of IgG4-related hypophysitis was made, and the patient was recommenced on prednisolone 50mg daily with plan to continue for 3 months before tapering.

Discussion: IgG4-related hypophysitis is rare fibroinflammatory disease characterised by dense lymphoplasmacytic infiltrate rich in IgG4+ plasma cells. This condition affects more males than females, often presents in the 6^th-7^th decade of life with varying degrees of hypopituitarism and/or diabetes insipidus. IgG4-related disease often involve other organs.

Diagnosis is made based on the following criteria:

1. Histopathological findings on pituitary biopsy or
2. MRI pituitary features (bulky stella mass with thickened pituitary stalk) plus histological evidence of extra-pituitary IgG4 related disease or
3. MRI pituitary features plus elevate serum IgG4 and evidence of steroid responsiveness

 Glucocorticoid is first line therapy for IgG4-related hypophysitis. Early treatment may reduce pituitary mass but may not reverse existing endocrinopathy.