Case Presentation: An 8-year old previously healthy boy presented with mutism. One week prior to admission, he developed chills, nausea, vomiting, night sweats, and a fever. Subsequently, he developed a headache, nuchal rigidity, ataxia, and staring spells. Upon presentation, he was afebrile with otherwise normal vitals. He was alert and followed commands with intact comprehension and fluent writing. He would not speak and rarely opened his eyes. His white blood cell (WBC) count was elevated to 14.8 x 103/µL. Comprehensive metabolic panel, urine cultures, and blood cultures were unremarkable. His cerebrospinal fluid (CSF) had a WBC count of 427 cells/µL (92% lymphocytes), red blood cell count of 157 cells/µL, protein of 150 mg/dL, and glucose of 51 mg/dL. Brain MRI demonstrated hyperintensity of the cerebellar cortex, concerning for cerebellitis. He was started empirically on ceftriaxone, vancomycin, and acyclovir, with improved comprehension, but he continued to only communicate through writing and hand squeezing. Ceftriaxone and vancomycin were discontinued with negative CSF cultures. Electroencephalogram revealed no seizure-like activity. Polymerase chain reactions for Herpes Simplex Virus, Enterovirus, Arbovirus, and West Nile Virus were negative. Epstein Barr Virus serology was also negative. Mycoplasma (M.) pneumoniae IgM immunofluorescent antibody returned positive. He was started on azithromycin to treat M. pneumoniae, and continued acyclovir for suspected viral meningoencephalitis. Days later, he recovered from his mutism and staring spells.

Discussion: M. pneumoniae is a common bacteria that typically manifests itself as an atypical pneumonia or respiratory disorder. Rarely, M. pneumoniae has been described as the causative organism in a number of neurologic manifestations, including encephalitis and acute disseminated encephalomyelitis. A few cases have reported a likely correlation of the anti-Galactocerebroside C (anti-Gal C) antibody induced by Mycoplasma infection with its neurologic pathogenesis. This patient was diagnosed with meningoencephalitis by a positive M. pneumoniae IgM; however, he lacked preceding or concurrent respiratory symptoms.  Instead, he had cerebral mutism, a complex including one of more findings of decreased speech, ataxia, difficulty with coordination, and hypotonia.  Only one published case has linked Mycoplasma to akinetic mutism in a pediatric patient, but our patient’s communication-based mutism is unique to the literature. The patient’s resistance to eye opening can be an assumed consequence of the photophobia that accompanies bacterial meningitis.

Conclusions: In cases of aseptic meningitis refractory to antiviral therapy, screening for atypical organisms including M. pneumoniae is worthwhile, particularly in the pediatric population. Though uncommon, M. pneumoniae should be considered on the differential for encephalitis when other common organisms have been ruled out.