肺炎支原体：儿童脑炎的最常见病原？

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Mycoplasma Pneumoniae: The Most Common Cause of Pediatric Encephalitis?
肺炎支原体：儿童脑炎的最常见病原？

Summary
摘要

This report details data collected as part of the California Encephalitis Project, begun in 1998. The current study patients represent those reported to the project from 1996-2006. Among many pathogens identified, Mycoplasma pneumoniae was the most common cause of encephalitis.
该报告将始于1998年的加利福尼亚脑炎项目的数据详细阐述。目前项目中的研究对象来自于1996年至2006年间纳入的人群。在很多鉴别出的病原体中，肺炎支原体是脑炎最常见的病原。

The authors completed this report to detail the history, physical, and laboratory findings of the children with M pneumoniae encephalitis in order to better understand the epidemiology of the process.
作者完善这项报告以进一步配合肺炎支原体脑炎患儿的病史、体检实验室检查，就是为了更好的明确该过程的流行病学。

Cases were defined as patients with encephalitis and evidence of acute infection with M pneumoniae: those with positive serum IgM or rising IgG antibodies to M pneumoniae, or subjects with a positive polymerase chain reaction to M pneumoniae from either the spinal fluid or respiratory sample.
肺炎支原体脑炎的定义包括两个方面，一是脑炎明确存在，二是有支原体急性感染的证据：或者是血清肺炎支原体IgM阳性，或是IgG上升，或者是脑脊液或呼吸道标本PCR阳性。

There were 1988 subjects in the project sample, and 111 (5.6%) had evidence of acute M pneumoniae infection. The majority of the patients (n = 84 [76%]) with M pneumoniae were younger than 19 years of age, with a median age of 11 years for those with M pneumoniae encephalitis. There were no gender differences.
项目共纳入了1988名对象的标本，其中111名（5.6%）存在急性肺炎支原体感染的证据，这其中的大多数(n = 84 [76%])患者小于19岁，患有肺炎支原体脑炎的患儿中位数年龄为11岁。不存在性别差异。

Many of the patients had gastrointestinal symptoms (45%), but an almost equal percentage had respiratory symptoms. Only 15% of the adults with M pneumoniae encephalitis had gastrointestinal symptoms. Of the pediatric patients with M pneumoniae encephalitis, most (n = 59 [70%]) were diagnosed by virtue of an elevated serum IgM to M pneumoniae. An additional 19 pediatric cases had IgM values that were positive along with another marker (such as respiratory polymerase chain reaction (PCR), serum IgG change, etc).
很多患者存在消化道症状（45%），几乎差不多比例的人群存在呼吸道症状。但成人肺炎支原体脑炎中只有15%存在消化道症状。儿童患者中，大多数(n = 59 [70%])是通过升高的血清肺炎支原体IgM诊断的。另外有19名患儿除了存在IgM升高之外，还存在另一项标记阳性（比如呼吸道PCR血清IgG变化等）。

Only 1 subject with M pneumoniae encephalitis had a positive cerebrospinal fluid (CSF) PCR for M pneumoniae. Nine percent of child cases had respiratory PCR positive for M pneumoniae. The median CSF white blood cell count was 33/mm3 among the patients with M pneumoniae encephalitis.
只有1名肺炎支原体脑炎患者出现脑脊液PCR阳性。9%患儿的呼吸道肺炎支原体PCR阳性。在肺炎支原体脑炎的患者中，平均脑脊液白细胞数是33/mm3。

Overall, however, the CSF values for patients with M pneumoniae encephalitis did not differ from those of other etiologies. Magnetic resonance imaging demonstrated abnormalities in 49% of the M pneumoniae cases.
总体来讲，该类患者的脑脊液的诊断价值与其他的方法没有明显的差别，MRI反映出49%患者的脑部异常。

Fourteen percent of the patients suffered coma, and 4% of the M pneumoniae child cases died. The authors note that M pneumoniae was the identified agent twice as often as enterovirus among children and 7 times as often as herpes simplex virus, type 1.
14%患者出现昏迷，4%的患儿死亡。作者指出，在患儿鉴别出的病原中，肺炎支原体是肠病毒的2倍，是一型单纯疱疹病毒的7倍.

The authors conclude that M pneumoniae was the most common causative agent identified in this series of patients, but CSF evidence of the infection is not usually found.
作者最后得出结论，肺炎支原体是这些患者最常见的病因，但是脑脊液的感染证据不常见。

Viewpoint

The lesson of this article is that serum samples, usually IgM and a combination of IgM and IgG (acute and convalescent titers), are the best methods to make the diagnosis of M pneumoniae encephalitis. A second message is that the symptoms of these patients are so similar to those seen in other etiologies that M pneumoniae might not immediately come to mind during consideration of the differential; M pneumoniae has to be on the list of \"usual suspects,\" or clinicians will likely greatly underdiagnose it in encephalitis cases. Finally, the authors note that the role of antibiotics in M pneumoniae encephalitis is not clear, primarily because it is not clear whether the CNS manifestations in M pneumoniae patients are the result of direct invasion or an autoimmune process which might not be improved directly by antibiotics.
观点
该研究的结论之一就是，血清IgM或者是联合 IgM 和 IgG是诊断肺炎支原体脑炎的最好方法。结论之二是该类脑炎的症状与其他病原体引起的脑炎非常相似，所以在鉴别诊断的时候，可能不会及时察觉，临床医生必须将它考虑在常见病因中，否则很可能就会漏诊。最后，作者指出，抗生素在该类脑炎中的作用还不是很清晰，主要是因为，对于该类患者出现的神经系统症状，还不明确是因为直接的侵犯还是因为继发的免疫反应，后者是不会因为抗生素的使用而改善的。