3. Discussion
In this case report, we present a middle-aged adult patient with BE associated with M. pneumoniae infection, diagnosed via positive IgM tests and increased levels in acute and convalescent sera with an EIA. The patient was successfully treated with clarithromycin and intravenous immunoglobulin.
M. pneumonia is well known to cause respiratory tract disease and extrapulmonary manifestations are also common3. It is frequently associated with encephalitis, especially in children. Lerer and Kalavsky found that 53 % of patients with CNS disease associated with M. pneumoniae were aged between 6 and 20 years4. In adults above middle ages, only a few cases have been reported, and one of these patients took an immunosuppressive agent5-7. Encephalitis caused by M. pneumoniaecannot be reliably diagnosed in adults, because the incidence rate is low and there are no clinical or radiologic signs indicating a mycoplasma etiology of CNS disease in addition to the absence of a clear diagnostic marker in CSF. The detection rate of M .pneumoniae by PCR in the CSF of M . pneumoniaeencephalitis patients is relatively low (0–14 %), and serologic tests are indispensable2. In addition, due to the high prevalence of M . pneumoniae infection, one measurement of high serum antibody titers may simply indicate carriage or a previous infection8. A reliable diagnosis may be achieved by using paired patient sera in order to detect seroconversion and/or increase in antibody titers. The gold standard is a four-fold increased Ig titer in partial agglutination assays or complement fixation tests.2 An EIA test can detect IgG and IgM separately to distinguish current from past infections. Several commercial EIA kits are now available and in some studies, the EIA method had moderate to high sensitivity and specificity.2 Furthermore, correlation of M. pneumoniae IgM values obtained by various IgM assays with particle agglutination assay titers was also noted.9 In our case, the level of IgM was increased in paired sera and the diagnostic value of an increasing titer should be validated in additional validation studies.
The pathogenesis of encephalitis associated with the respiratory pathogen M. pneumoniae is not well understood. A direct infection of the CNS and an immune-mediated process have been discussed.2 Considering several cases of Guillain-Barré syndrome10, Bickerstaff brainstem encephalitis11, and N-methyl-D-aspartate receptor associated with Mycoplasma spp. Infection12, the immune response to M. pneumoniae in the CNS can be an important factor that contributes to encephalitis.6 Therefore, the development of new diagnostic tools, such as the detection of antibodies against M. pneumoniae in the CSF is necessary.
M . pneumoniae lacks a cell wall and beta-lactate antibiotics are not suitable to treat the infection. Doxycycline, a macrolide can be used and corticosteroids may be beneficial according to a recent review of severe cases.2
We diagnosed BE associated M. pneumoniae infection through EIA with an increasing titer of IgM in acute and subacute paired sera. The early treatment with macrolide antibiotics resulted in a good outcome for our patient. IV immunoglobulin was administrated for five days and might have supported the recovery. Considering the pathogenesis of immune-mediated processes, it will be necessary to conduct further studies on the efficacy of immunomodulatory treatment.
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Conflicts of interest: None