Atypical pneumonia (non-COVID-19)

Community-acquired and often seen in young adults living in close proximity.

Diagnosis is mostly clinical. Molecular-based diagnosis of throat swabs or sputum can be performed. Serology can be used to confirm the diagnosis.

Treatment is often outpatient based with a macrolide antibiotic or doxycycline.

Extrapulmonary manifestations may occur, especially in Mycoplasma pneumoniae infections.

Atypical bacterial pneumonia is caused by atypical organisms that are not detectable on Gram stain and cannot be cultured using standard methods. The most common organisms are Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila. Atypical bacterial pneumonia generally is characterized by a symptom complex that includes headache, low-grade fever, cough, and malaise. Constitutional symptoms often predominate over respiratory findings. Although in most cases presentation can be in the milder spectrum of community-acquired pneumonia, some cases, especially if caused by L pneumophila, may present as severe pneumonia, necessitating intensive care unit admission. Other possible pathogens include Chlamydophila species, Legionella species, Coxiella burnetii (Q fever), and respiratory viruses.