Intraocular plasmacytoma: A case of iris involvement and a review of the literature

Purpose: Describe a case of intraocular plasmacytoma in a patient with multiple myeloma successfully treated with photon irradiation. Observations: A 61-year-old man with a history of relapsing/refractory multiple myeloma and left frontal bone plasmacytoma treated with monthly belantamab mafodotin salvage chemotherapy developed bilateral treatment-related corneal keratopathy. An iris mass was incidentally noted in the right eye during a follow-up examination. The mass was amelanotic with diffuse intrinsic vasculature involving the pupillary margin from 1:30 to 10:30. Fundus examination showed an irregularly shaped amelanotic superotemporal scleral lesion in the right eye and two smaller amelanotic scleral lesions in the left eye. Given known systemic multiple myeloma and history of left frontal bone plasmacytoma, a presumed diagnosis of iris and scleral plasmacytoma was made. Due to rapid progression of the iris plasmacytoma despite systemic chemotherapy, the patient was treated with 20 Gy photon irradiation to the anterior and posterior segments of both eyes. One month after photon irradiation, there was complete regression of the iris plasmacytoma, and the scleral lesions in both eyes also appeared to be regressing despite systemic progression of multiple myeloma. Conclusions and importance: Intraocular plasmacytoma is rare and can occur in isolation but typically occurs as a manifestation of systemic multiple myeloma. Intraocular plasmacytoma can be successfully treated with photon irradiation in patients with multiple myeloma who progress on systemic chemotherapy.