The term "atypical pneumonia" is a general reference to any pneumonia that is unusual in terms of the causative infectious germ, the symptoms or the clinical course. Medical professionals sometimes use the term to refer specifically to pneumonias caused by Chlamydophila pneumoniae, Mycoplasma pneumoniae or Legionella pneumophila. Some may also include viral pneumonias under the category of atypical pneumonia. The imprecision of the term atypical pneumonia is mirrored by the indistinct symptoms of these infections, which often overlap with one another and other illnesses.
Fever
Fever may occur with any of the atypical pneumonias, although this symptom is not uniformly present. High fever and chills may occur with Legionella pneumophila infection, more commonly known as Legionnaire's disease, reports the University of Pennsylvania Health System. Mycoplasma pneumoniae can also cause a high fever in some patients, although low-grade fever is more common.
Muscle Aches
Muscle aches may accompany the three bacterial causes of atypical pneumonia, note Drs. Kristopher Thibodeau and Anthony Viera in a 2004 article published in "American Family Physician." Viral causes of atypical pneumonia, such as the influenza viruses, also commonly cause this symptom.
Cough
Cough characteristically occurs with all forms of pneumonia, including the atypical pneumonias. A distinctive feature of Legionnaire's disease is the high probability of coughing up blood with this infection, as noted on MedlinePlus. Blood-streaked phlegm does not typically occur with other forms of atypical pneumonia.
Sore Throat
Thibodeau and Viera note that sore throat may occur with atypical pneumonia caused by Chlamydophila pneumoniae or Mycoplasma pneumoniae, but does not typically present with Legionnaire's disease. Notably, sore throat may be a feature of viral pneumonia.
Skin Rash
A potentially distinguishing characteristic of atypical pneumonia caused by Mycoplasma pneumoniae is the development of a skin rash, reports the University of Maryland Medical Center. Other types of atypical pneumonia do not typically cause a skin rash.
Abdominal Pain and Diarrhea
Abdominal pain and diarrhea commonly occur with Legionnaire's disease, reports the University of Pennsylvania Health System. Mild diarrhea sometimes occurs with Mycoplasma pneumoniae infection of the lungs. Gastrointestinal symptoms, however, are generally absent with other forms of atypical pneumonia.
Fatigue and Malaise
Fatigue and malaise---a sense of feeling ill---may accompany any form of typical or atypical pneumonia, notes The Merck Manual for Healthcare Professionals. The severity of these symptoms varies from one individual to another and cannot be used to differentiate the underlying cause of the pneumonia.
Rapid Breathing and Shortness of Breath
Rapid breathing and shortness of breath are common symptoms of atypical pneumonia, notes the University of Pennsylvania Health System. Notably, these symptoms are not specific to atypical pneumonia and may occur with other forms of pneumonia and an array of diseases that affect the lungs and heart.
References
- Penn Medicine: Atypical Pneumonia
- Penn Medicine: Legionnaire's Disease
- "American Family Physician"; Atypical Pathogens and Challenges in Community-Acquired Pneumonia; Kristopher P. Thibodeau, M.D., Anthony J. Viera, M.D.; April 2004
- MedlinePlus: Legionnaire's Disease
- University of Maryland Medical Center: Mycoplasma Pneumonia
