[Atypical encephalitis in a 20-year-old soldier].

We report a patient with encephalitis who had been diagnosed with an unspecific aetiology. During follow-up, pneumonia was identified due to Mycoplasma pneumoniae infection that could also be confirmed as causal for the brain inflammation. Despite the initially critical clinical situation, the patient's condition improved under specific antibiotic treatment. Pathophysiologic, differential diagnostic, and therapeutic implications are discussed, and guidelines for diagnosis are proposed.