Optic nerve head plasmacytoma as a manifestation of multiple myeloma.

Extramedullary disease in multiple myeloma is uncommon and associated with a poorer prognosis. Extramedullary disease involving the orbit is even more unusual, with optic nerve involvement being rare. We describe an optic nerve head plasmacytoma in a 45-year-old female in the setting of systemic relapsed, refractory IgA kappa multiple myeloma. The case highlights the importance of keeping extramedullary disease spread in the differential for vision loss in a patient with a history of multiple myeloma. In addition, it describes an unusual location for presentation of extramedullary disease, the optic nerve head, which has rarely been described.