Bilateral Proptosis in a Case of Recurring Multiple Myeloma: Uncommon Orbital Presentation of Plasmacytoma.

Multiple myeloma is a malignant plasma cell dyscrasia that may invade the orbits in extramedullary presentations. Common manifestations of orbital involvement include unilateral proptosis, injection, chemosis, diplopia, and occasionally pain. Additionally, the soft-tissue tumors associated with multiple myeloma typically cause bony destruction of adjacent structures. However, in certain patients, bilateral proptosis and a lack of bony destruction may occur. In these instances, it is important for physicians to consider patient history, presentation, and progression in order to ensure that a potentially fatal diagnosis is not missed. The reason this case is important is two-fold: 1) we describe a case of an individual with relapsing multiple myeloma presenting as bilateral proptosis and lacking bony destruction, highlighting the importance of understanding the disease process and 2) we discuss why patients with multiple myeloma may be more prone to developing tumors of the orbit in recurrent cases.