Mycoplasma pneumoniae: Innocent Bystander or a True Cause of Central Nervous System Disease?

Abstract

The consistency with which Mycoplasma pneumoniae has been implicated as a cause of encephalitis, and the increased incidence of central nervous system (CNS) disease observed during M. pneumoniae respiratory outbreaks, support the role of M. pneumoniae as a CNS pathogen. Three pathophysiologic mechanisms have been proposed: direct infection, autoimmunity, and vascular occlusion. Recent evidence demonstrating the organism's ability to survive intracellularly, presence of its DNA in the serum of individuals with acute encephalitis, case reports in which the organism is detected in brain parenchyma or cerebrospinal fluid (CSF), and animal data demonstrating CNS invasion by several Mycoplasma species support the contention that M. pneumoniae is capable of direct infection of the CNS. Because of limitations of current serologic assays and difficulty in interpreting the significance of positive polymerase chain reaction results in regard to acuity of infection and viability of the organism, the diagnosis of M. pneumoniae-associated CNS disease should be based on a combination of positive tests and exclusion of alternative diagnoses.

Mycoplasmal panencephalitis: a neuropathologic documentation

“…PCR studies, mostly of CSF, suggest that those patients with early-onset ''encephalitis'' (i.e., neurological onset within 7 days of fever) is thought to be due to a direct infection of CSF or brain tissue, whereas those with later onset ''encephalitis'' are considered to be mediated by immune or vascular pathomechanisms (reviewed in Refs. [3,8,11]). Our patient, who developed encephalitic symptomatology 7 days after the onset of fever, exhibited neuropathologic evidence of direct infection of brain cells at autopsy, confirming those PCR studies.…”

“…In spite of these latter shortcomings, three pathogenetic mechanisms have been proposed for extrapulmonary neurological disease: direct infection, autoimmunity, and vascular occlusion (reviewed in Refs. [3] and [8]). …”

Corticosteroid Treatment in Autoimmune Encephalitis

“…We recommend that testing be performed in pediatric patients and include both serology and PCR analysis. Overall, the strength of microbiologic evidence needs to be considered when implicating M. pneumoniae as the cause of encephalitis [51].…”

An Encephalitis Primer

“…In some studies of encephalitis M. pneumoniae has accounted for 5-13 % of cases [24,25]. It's relative rarity in other studies may relate to limitations of current diagnostic methods [26] and also the occurrence of disease in cycles (3-4 years in the UK) longer than most epidemiological studies [27]. The detection of organisms via culture or PCR in CSF suggests that direct invasion of the central nervous system plays an important role in pathogenesis in at least some individuals [24,26].…”

“…It's relative rarity in other studies may relate to limitations of current diagnostic methods [26] and also the occurrence of disease in cycles (3-4 years in the UK) longer than most epidemiological studies [27]. The detection of organisms via culture or PCR in CSF suggests that direct invasion of the central nervous system plays an important role in pathogenesis in at least some individuals [24,26]. However immunological mechanisms are likely to be important in many children including cases of ADEM [28].…”