Retinal neovascularization in the setting of CALR-mutation positive essential thrombocythemia

Patients with Calreticulin (CALR) mutation positive essential thrombocythemia are often thought of as having a "low-risk" of thrombotic complications. This report examines a case of a patient with CALR-mutation positive essential thrombocythemia presenting with peripheral retinal ischemia and subsequent retinal neovascularization. This patient had a 2-year documented history of CALR-mutation positive essential thrombocythemia with a maximum platelet count of over 800,000 cells/µL. Fluorescein angiogram showed significant leakage in the areas of the vascular lesions with peripheral vascular nonperfusion consistent with neovascularization. The patient was treated with photocoagulation to the areas of avascular retina. At 6-month follow-up, some regression of neovascularization was noted with no signs of progression in the retinopathy. Furthermore, essential thrombocythemia patients can present with neovascularization secondary to retinal ischemia due to microvascular thrombotic events. Identification of these changes is important for guiding medical and procedural interventions in order to preserve vision.