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.
Financial support : None
Conflicts of interest: None