患男,41岁,以发热、消瘦、多饮、多尿1月为主诉入院。1月前无任何诱因出现间歇性发热,下午多见,自测体温37.2～38.5℃,伴有多饮、多尿、口渴,逐渐消瘦,偶有头痛及双上肢麻木感。每d饮水量2500～3000ml,尿量4000～7000ml。曾按“散发性脑炎”住院治疗2周,症状缓解。1周前上述症状再次出现,头痛较前加重,来我院以“发热伴脱水待诊”入院。查体:T36.5℃,P80次/min,BP15/10kpa,体重41.5kg。神志清楚,消瘦明显,表情淡漠,无欲状,皮肤干燥,无弹性。回答切题,双侧瞳孔等大等圆约3mm,对光反射灵敏。颈软,无抵抗。心、肺、腹(-)。神经系统检查:颅神经征(-),四肢肌力、肌张力正常,膝腱反射(),双侧巴氏征(-),脑膜刺激征(-)。实验室 Suffering from men, 41 years old, with fever, weight loss, polydipsia, polyuria January main admission. 1 month ago without any incentive intermittent fever, more common in the afternoon, self-test temperature 37.2 ~ 38.5 ℃, accompanied by polyhydration, polyuria, thirst, gradually weight loss, occasional headache and upper limb numbness. Each d drinking 2500 ~ 3000ml, urine output 4000 ~ 7000ml. According to “sporadic encephalitis” hospitalized for 2 weeks, the symptoms ease. A week ago, the above symptoms reappeared, the headache worsened earlier, to our hospital with “fever with dehydration pending diagnosis” admission. Physical examination: T36.5 ℃, P80 times / min, BP15 / 10kpa, weight 41.5kg. Conscious, wasting significantly, expression indifference, no desire, dry skin, inelastic. Answer the question, bilateral pupils and other large round about 3mm, sensitive to light reflection. Soft neck, no resistance. Heart, lung, belly (-). Nervous system examination: cranial nerve sign (-), limb muscle strength, normal muscle tone, knee tendon reflexes (), bilateral Pakistan’s sign (-), meningeal irritation sign (-). laboratory