33 A Rare Case of Idiopathic Multicentric Castleman Disease with Ocular Involvement

Introduction/Objective Idiopathic multicentric Castleman disease (iMCD) is a benign lymphoproliferative disorder with uncertain etiology, as opposed to other forms such as Kaposi sarcoma-associated / human herpesvirus 8 (KSHV/HHV8)-associated multicentric Castleman disease which have category-defining etiologies. While iMCD most commonly affects the spleen and lymph nodes, we report here a rare case of iMCD with ocular involvement. Methods/Case Report A 30-year-old male presented with diplopia, blurry vision, and left-sided exophthalmos for two weeks and several months of cervical and axillary lymphadenopathy. Imaging revealed bilateral orbital masses with extraocular muscle and lacrimal gland involvement. The patient’s bone marrow was biopsied, revealing a polytypic plasmacytosis without an abnormal IgG:IgG4 ratio, in a background of normocellular marrow with trilineage hematopoiesis. Biopsies of the left orbital fat pad and axillary lymph nodes revealed a similar polytypic plasmacytosis, and serological testing revealed an abnormal increase in autoimmune markers. Repeat axillary lymph node biopsy revealed atrophic, twinning germinal centers and increased vascularity, along with the similar polytypic plasmacytosis. Subsequent Interleukin-6 and Vascular Endothelial Growth Factor levels were found to be elevated, supporting a final diagnosis of iMCD. Results NA Conclusion Idiopathic MCD rarely presents with ocular involvement and can present diagnostic challenge due to heterologous presentation and overlapping features with other diseases.