Bacterial infections in the lungs of patients with systemic autoimmune diseases

In patients with systemic autoimmune diseases (such as systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, Sjogren syndrome, polymyositis/dermatomyositis, and antineutrophil cytoplasmatic autoantibody-related vasculitis), pneumonia is one of the most common complications and an important cause of hospitalization, morbidity, and mortality. These patients may be more susceptible to bacterial infection of the lungs because of impaired host defenses associated with the disease itself (immune system alterations and organ damage) and the effects on the immune response to bacteria of concomitant immunosuppressive therapy. Cigarette smoking cessation and vaccination against Streptococcus pneumoniae and Haemophilus influenzae type B are recommended. There are no standardized protocols for the diagnosis, differential diagnosis, and the treatment of pneumonia in these patients. Current best practice is to follow national and international guidelines on community-acquired pneumonia, hospital-acquired pneumonia, aspiration pneumonia, and pneumonia in specific cases of immunocompromission, even though the precise causative pathogen will be unknown.