Legionnaire's disease (LD) is most commonly caused by Legionella pneumophila (L. pneumophila). In immunocompromised patients LD can cause necrosis of the lung parenchyma with abscess formation and cavitation. Systemic lupus erythematosus (SLE) is an autoimmune disorder with features of both primary and secondary immunodeficiency. SLE patients often develop pulmonary abnormalities, but rarely develop lung cavitations. We report a case of cavitary pneumonia caused by L. pneumophila in a 64-year-old female patient with SLE. We also highlight reasons why SLE patients are more prone to L. pneumophila infections. The importance of using correct diagnostic methods for recognizing and treating such infections is also discussed, as mistreatment of cavitary lesions in SLE patients with steroid therapy can have fatal outcomes as the infectious process can significantly worsen.
