Following an overview of the definition of autism and Lyme disease, a clinical case will be presented of a young subject (aged 14 years and a half) diagnosed with autism, and characterized by a typical development in the first year of life, followed by a general deterioration of abilities shortly after diagnosis of the onset of Lyme disease. The subject presented positive reactivity for Mycoplasma Pneumoniae. According to recent studies, misdiagnosis of initial symptoms of Lyme disease and delayed treatment can lead to persistent interactive coinfections in the organism which may result in chronic pathologies. Thus, a link could exist between a chronic infectionwith Mycoplasma Pneumoniae and an atypical symptomology similar to autism. So the hypothesis proposed is that there may be a correlation between Lyme disease and autism and that long-term antibiotic therapy may be an effective treatment. Following a clinical presentation of the history of this young patient, the evolution of the subject's symptomology and behavior during one year of antibiotic therapy will be described.