Essential thrombocythemia (ET) presenting as a combined cilioretinal artery occlusion (Cil.RAO) and central retinal vein occlusion (CRVO)

A 35-year-old male presented with sudden vision loss in his left eye for 1 day and was diagnosed with combined cilioretinal artery occlusion (Cil.RAO) and central retinal vein occlusion (CRVO). A multidisciplinary clinical work up was conducted to determine the underlying cause. A full blood count revealed a very high platelet count (1,147,000/mm 3 ), prompting further hematologic investigation. Peripheral blood smear showed abundant platelet clumps, and bone marrow trephine biopsy indicated megakaryocytic hyperplasia and reticulin fibrosis (grade 1). The patient tested heterozygous for the JAK2 V617F mutation, a genetic marker for myeloproliferative disorders, and was diagnosed with essential thrombocythemia (ET). After a month of treatment with hydroxyurea 500 mg daily, his platelet count returned to normal. Thrombocythemia is associated with systemic and ocular thrombotic and embolic complications. A full blood count was pivotal in diagnosing and managing ET in this patient with combined retinal vascular disease.