Estrella lausannensis, a Chlamydia-related bacterium isolated from a Spanish river, is considered as a possible emerging human pathogen. Indeed, it was recently demonstrated to multiply in human macrophages, resisting oxidative burst and causing a strong cytopathic effect. In addition, a preliminary study highlighted a correlation between antibody response to E. lausannensis and pneumonia in children. To clarify the pathogenic potential of these bacteria, we infected a human pneumocyte cell line with E. lausannensis and assessed its replication and cytopathic effect using quantitative real-time PCR and immunofluorescence, as well as confocal and electron microscopy. Our results demonstrated that E. lausannensis enters and replicates rapidly in human pneumocytes, and that it causes a prompt lysis of the host cells. Furthermore, we reported the spontaneous formation of aberrant bodies, a form associated with persistence in Chlamydiae, suggesting that E. lausannensis infection could cause chronic disorders in humans.