原發性血小板增多症的臨床表徵並不典型且早期診斷不易，往往多數病人於診斷前已發生動靜脈血栓形成及出血併發症。本個案一位72歲女性，有高血壓及胃食道逆流病史並按時門診追蹤服藥，五天前注射新冠疫苗後，呼吸喘、乾咳併胸悶至診所就醫未改善，於急診初步診斷急性支氣管炎。入院後感心悸且胸悶，藉由病史詢問、檢驗及理學檢查，顯示心肌酵素正常但心電圖呈現陣發性心室上心搏過速，安排冠狀動脈血管攝影攝影後排除急性心肌梗塞，但呼吸急促未見好轉呈現低血氧，經胸腔電腦斷層為肺栓塞。疑似新冠疫苗後引起的免疫併發症，直到右手食指及中指末梢腫、痛且發紺症狀出現，筆者再次重新檢視病史資料，發現血小板異常，透過骨髓穿刺切片是發現巨核細胞（megakaryocyte）增生，病理報告判斷為骨髓增生性腫瘤，基因檢測結果為JAK2V617F 突變，最後確診是原發性血小板增多症併發肺栓塞，接受Hydroxyurea合併口服抗凝血劑治療，症狀改善且血小板數值趨於穩定。藉此案例分享提醒當發現病人有不明血栓產生時須考慮將相關血液疾病列入鑑別診斷，期能及早發現疾病，掌握治療時機。

The clinical symptoms of essential thrombocythemia are not typical and early diagnosis is difficult.Most patients have arteriovenous thrombosis and bleeding complications before diagnosis. In this case, a 72-year-old woman had a history of hypertension and gastroesophageal reflux and was taking medication regularly at the outpatient clinic. After being injected with the COVID-19 vaccine five days ago, her breathing, dry cough, and chest tightness did not improve when she went to the clinic. She was initially diagnosed with acute bronchitis in the emergency department. After being admitted to the hospital, she felt palpitations and chest tightness. The medical history, examination and physical examination showed that myocardial enzymes were normal, but the electrocardiogram showed Parox-ysmal supraventricular tachycardia. Coronary angiography was arranged to rule out acute myocardial infarction, but the shortness of breath persisted with hypoxemia, and the computed tomography of the chest showed pulmonary embolism. Immune complications caused by the COVID-19 vaccine were suspected, symptoms of swelling, pain and cyanosis appeared in the distal part of the right index fin-ger and middle finger appeared. The author re-examined the medical history data and found abnormal platelets. Through bone marrow aspiration and sectioning, megakaryocyte hyperplasia was found. Pa-thology report determined that the patient suffered from myeloproliferative neoplasm, and the genetic test result was the JAK2V617F mutation. The patient was finally diagnosed with essential thrombocythe-mia complicated by pulmonary embolism. She was treated with Hydroxyurea combined with oral an-ticoagulants. The symptoms improved and the platelet level stabilized. This case serves as a reminder that when a patient is found to have unknown thrombosis, related blood diseases must be considered in the differential diagnosis, so that the disease can be detected early and proper treatments can be pro-vided.