Hypophysitis Secondary to Small Vessel ANCA Vasculitis Treated With Rituximab

Background/objectiveAntineutrophil cytoplasmic antibody (ANCA) associated vasculitis is a rare small vessel vasculitis that can cause pituitary hypophysitis. Hypophysitis is difficult to treat, often requiring high doses of glucocorticoids and with frequent flaring as glucocorticoids are tapered. We present a case of ANCA vasculitis involving the pituitary gland successfully treated with rituximab.Case Report51-year-old woman developed progressive frontal headaches, congestion, and epistaxis. Sinus computed tomography (CT) scan showed pituitary enlargement and chronic mucosal disease. Pituitary magnetic resonance imaging (MRI) confirmed a diffusely enlarged pituitary with a thickened pituitary stalk. Serologic evaluation revealed elevated inflammatory markers, positive perinuclear ANCA (p-ANCA), and elevated serum anti-proteinase 3 (anti-PR3) antibody. The patient underwent pituitary biopsy which showed adenohypophysitis with dense lymphoplasmacytic infiltration, some arranged perivascularly, compatible with involvement of the pituitary gland by ANCA vasculitis. The patient began rituximab and reported resolution of daily headaches, congestion, and epistaxis. Pituitary MRI six months after rituximab showed reduction in pituitary gland size and stalk thickening.DiscussionANCA vasculitis is a rare etiology of pituitary hypophysitis, which can present a diagnostic and therapeutic challenge. Pituitary involvement of ANCA vasculitis can be identified through p-ANCA or cytoplasmic ANCA (c-ANCA) and biopsy of involved tissue. Rituximab, a monoclonal antibody against CD20, has been successfully used to treat ANCA vasculitis and in this case, led to clinical improvements and reduction in size of the pituitary gland.ConclusionPituitary biopsy enabled confirmation of ANCA hypophysitis and facilitated treatment with a steroid sparing agent.