在大部分研究中,感染性疾病是最常见病因,其次是恶性肿瘤,自身免疫疾病或其他病因。[6]De Kleijn EM, Vandenbroucke JP, van der Meer JW. Fever of unknown origin (FUO). I A. prospective multicenter study of 167 patients with FUO, using fixed epidemiologic entry criteria. Medicine (Baltimore). 1997 Nov;76(6):392-400.http://www.ncbi.nlm.nih.gov/pubmed/9413425?tool=bestpractice.com[7]Knockaert DC, Vanneste LJ, Bobbaers HJ. Recurrent or episodic fever of unknown origin. Review of 45 cases and survey of the literature. Medicine (Baltimore). 1993 May;72(3):184-96.http://www.ncbi.nlm.nih.gov/pubmed/8502169?tool=bestpractice.com
感染
FUO 最常见的感染性原因是结核病、腹内脓肿及盆腔脓肿。[3]Hersch EC, Oh RC. Prolonged febrile illness and fever of unknown origin in adults. Am Fam Physician. 2014 Jul 15;90(2):91-6.http://www.aafp.org/afp/2014/0715/p91.htmlhttp://www.ncbi.nlm.nih.gov/pubmed/25077578?tool=bestpractice.com[4]Roth AR, Basello GM. Approach to the adult patient with fever of unknown origin. Am Fam Physician. 2003 Dec 1;68(11):2223-8.https://www.aafp.org/afp/2003/1201/p2223.htmlhttp://www.ncbi.nlm.nih.gov/pubmed/14677667?tool=bestpractice.com[5]Varghese GM, Trowbridge P, Doherty T. Investigating and managing pyrexia of unknown origin in adults. BMJ. 2010;341:C5470.http://www.ncbi.nlm.nih.gov/pubmed/22312655?tool=bestpractice.com FUO 在免疫功能低下患者(如患有HIV/AIDS,中性粒细胞减少或严重系统性疾病)中通常是难以诊断的问题。 针对免疫功能低下患者,许多机会性感染,恶性肿瘤和疾病自身的进程需要积极的评估和管理。[2]Durack DT, Street AC. Fever of unknown origin - reexamined and redefined. Curr Clin Top Infect Dis. 1991;11:35-51.http://www.ncbi.nlm.nih.gov/pubmed/1651090?tool=bestpractice.com
恶性肿瘤和自身免疫性疾病
随着发热持续时间增加,更有可能是恶性肿瘤或自身免疫性疾病。[8]Kazanjian PH. Fever of unknown origin: review of 86 patients treated in community hospitals. Clin Infect Dis. 1992 Dec;15(6):968-73.http://www.ncbi.nlm.nih.gov/pubmed/1457669?tool=bestpractice.com[9]Vanderschueren S, Knockaert D, Adriaenssens T, et al. From prolonged febrile illness to fever of unknown origin: the challenge continues. Arch Intern Med. 2003 May 12;163(9):1033-41.http://archinte.ama-assn.org/cgi/content/full/163/9/1033http://www.ncbi.nlm.nih.gov/pubmed/12742800?tool=bestpractice.com 最有可能导致 FUO 的恶性肿瘤包括白血病和淋巴瘤、肾脏细胞癌和转移癌。[7]Knockaert DC, Vanneste LJ, Bobbaers HJ. Recurrent or episodic fever of unknown origin. Review of 45 cases and survey of the literature. Medicine (Baltimore). 1993 May;72(3):184-96.http://www.ncbi.nlm.nih.gov/pubmed/8502169?tool=bestpractice.com 自身免疫疾病通常与不明原因发热有关,例如成人斯蒂尔 (Still's) 病、风湿性多肌痛、颞动脉炎、系统性红斑狼疮和炎症性肠病。
其他病因
包括药物引起的发热、肝炎和肝硬化、深静脉血栓形成、结节病、甲状腺疾病和中枢神经系统疾病。假热也可能是一个病因。体温受下丘脑调节,可受作用于前列腺素通路的广泛物质的影响。适度的体温升高可能是生理性的,例如对排卵或剧烈运动的反应。