女,31歲,三天來(lái)發(fā)熱,惡心、嘔吐,食欲減退,頭痛,四肢酸痛,腰痛。體檢:危重病容,球結(jié)膜充血,無(wú)水腫,咽充血,腋下可見(jiàn)點(diǎn)狀抓痕樣出血點(diǎn),肝脾未及。血常規(guī)檢查:WBC14×109/L,N72%,L28%,可見(jiàn)異型淋巴細(xì)胞。尿常規(guī):尿蛋白(+++),RBC4~5個(gè)/HP,該患者首先考慮的診斷為()