Complete resolution of advanced Mycoplasma pneumoniae encephalitis mimicking brain mass lesions: report of two pediatric cases and review of literature.

Mycoplasma pneumoniae is a well-known cause of atypical pneumonia. CNS involvement is a relatively frequent extrapulmonary manifestation, most commonly manifesting as encephalitis in the pediatric population. We present two unusual cases of M. pneumoniae encephalitis that presented with symptoms and imaging findings suggesting mass occupying lesions, and worsening altered mental status. Biopsy of the lesions was necessary in both cases to aid with diagnosis. Histopathologic features excluded neoplasm, and established the diagnosis of encephalitis, but did not point toward its etiology. The only finding that indicated M. pneumoniae as the most likely pathogen was serum IgM positivity in the absence of any other identifiable infectious source, and complete neurologic recovery following specific anti-mycoplasmal treatment. The patients were successfully treated with antibiotics and steroids, with the second case also requiring intravenous immunoglobulin and anti-epileptics. The clinical presentation and histopathologic findings suggested an immune-mediated pathogenesis, but acute disseminated encephalomyelitis was excluded due to extensive gray matter involvement. Disease resolution despite status epilepticus and herniation in case 2 is a novel finding of the study. Current principles of diagnosis and management of encephalitis as the presenting manifestation of mycoplasmal infection are discussed.

The new mycobacterial species--emerging or newly distinguished pathogens.

Diseases due to nontuberculous mycobacteria are increasing in frequency, especially in patients with compromised immunity. A number of "new" mycobacterial species have been described in the last decade, largely as the result of the use of new tools to identify previously unrecognized mycobacteria found in the environment and in clinical specimens. This article reviews many of these potentially pathogenic organisms, summarizing what is known regarding their phenotypic and genotypic characterization, antimicrobial susceptibility, and clinical significance.