FRI339 Hypophysitis Secondary To Small Vessel Anca Vasculitistreated With Rituximab

Abstract

Abstract Disclosure: A. Rivadeneira: None. N. Kumar: None. S. Banerjee: None. M. Gubbiotti: None. D. Yoshor: None. J. Kharlip: None. C.A. White: None. Introduction: Granulomatosis with polyangiitis (GPA) is an autoimmune small-vessel vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCAs) that rarely involves the pituitary. Conventional treatment of GPA includes high dose glucocorticoids with cyclophosphamide. Rituximab has been used in refractory cases with high rates of remission. We present a case of pituitary GPA treated with and excellent response to rituximab. Case: 51-year-old woman with hypothyroidism, post I-131 treatment for Graves’ disease. Patient presented with 1 year of worsening fatigue, myalgias, frontal headaches, sinus congestion and epistaxis. CT sinus showed pituitary enlargement and chronic mucosal disease. MRI pituitary showed diffusely enlarged pituitary with non-visualized posterior pituitary bright spot and thickened stalk. CT chest showed 18x11 mm nodular opacity and peribronchial fibrosis. Laboratory evaluation showed ACTH 26.7 pg/mL, cortisol 13.4 mcg/dL, TSH 1.1, T4 9.7, prolactin 53 ng/dL, estradiol <20, LH 4, FSH 23. Sodium 140 and urine osm 488. There was positive p-ANCA staining and elevated serum anti-proteinase 3 antibody (PR3), 74 units (0-20). Myeloperoxidase antibody was not elevated. ESR 73 mm/h (0 - 30) and CRP 7.9 (<7.4). Due to atypical ANCA pattern (p ANCA typically is associated with MPO not PR3), pituitary biopsy was performed and showed adenohypophysis with dense lymphoplasmacytic infiltration with nodularity of the inflammatory infiltrates, some arranged peri vascularly, compatible with involvement of the pituitary gland by GPA. She began rituximab 375 mg/m2 weekly for four weeks with plan to continue every 6 months. After treatment, the patient experienced resolution of daily frontal headaches, congestion, cough and epistaxis. CT chest showed improvement of prior lung findings, and ESR/CRP normalized. Repeat pituitary MRI is pending. Discussion: Pituitary involvement is uncommon in GPA, occurring in only 3.9% of cases. It may lead to partial or complete pituitary dysfunction, particularly central diabetes insipidus (87.5%) and hypogonadism (75%). Typical MRI abnormalities include diffusely enlarged pituitary gland, thickened pituitary stalk and absence of posterior bright spot. Treatment of GPA includes a combination of corticosteroids, Cyclophosphamide, Azathioprine and Rituximab. Remission is achieved in up to two thirds of patients. Treatment of lymphocytic hypophysitis, another common cause of diffuse pituitary enlargement, relies on high dose glucocorticoids, leading to many side effects and taper is limited by worsening symptoms. This case highlights the critical role in serologic evaluation and targeted pituitary biopsy to identify the specific etiology of pituitary infiltration to help guide alternate treatment options, and the emerging role of Rituximab as a steroid sparing agent for treatment of pituitary inflammation. Presentation: Friday, June 16, 2023