Atypical pneumonia
Atypical pneumonia | |
---|---|
Other names | Walking pneumonia |
Infectious disease, pulmonology |
Atypical pneumonia, also known as walking pneumonia,[1] is any type of pneumonia not caused by one of the pathogens most commonly associated with the disease. Its clinical presentation contrasts to that of "typical" pneumonia. A variety of microorganisms can cause it. When it develops independently from another disease, it is called primary atypical pneumonia (PAP).
The term was introduced in the 1930s
Signs and symptoms
Usually the atypical causes also involve atypical symptoms:
- No response to common antibiotics such as beta-lactams like penicillin.
- No signs and symptoms of lobar consolidation,[6][7] meaning that the infection is restricted to small areas, rather than involving a whole lobe. As the disease progresses, however, the look can tend to lobar pneumonia.
- Absence of leukocytosis.[citation needed]
- Extrapulmonary symptoms, related to the causing organism.[8]
- Moderate amount of sputum, or no sputum at all (i.e. non-productive).
- Lack of alveolar exudate.[9]
- Despite general
- Silent hypoxia may occur and not be noticed, but will be picked up by pulse oximetry.
Cause
The most common causative organisms are (often intracellular living) bacteria:[8]
- Chlamydia pneumoniae
- Mild form of pneumonia with relatively mild symptoms.
- Chlamydia psittaci
- Causes psittacosis.
- Coxiella burnetii
- Causes Q fever.
- Francisella tularensis
- Causes tularemia.
- Legionella pneumophila
- Causes a severe form of pneumonia with a relatively high mortality rate, known as legionellosisor Legionnaires' disease.
- Mycoplasma pneumoniae
- Usually occurs in younger age groups and may be associated with neurological and systemic (e.g. rashes) symptoms. See Mycoplasma pneumonia.
Atypical pneumonia can also have a fungal, protozoan or viral cause.[10][11]
In the past, most organisms were difficult to culture. However, newer techniques aid in the definitive identification of the pathogen, which may lead to more individualized treatment plans.[citation needed]
Viral
Known viral causes of atypical pneumonia include
Diagnosis
Chest radiographs (X-ray photographs) often show a pulmonary infection before physical signs of atypical pneumonia are observable at all.[5] This is occult pneumonia. In general, occult pneumonia is rather often present in patients with pneumonia and can also be caused by Streptococcus pneumoniae, as the decrease of occult pneumonia after vaccination of children with a pneumococcal vaccine suggests.[14][15]
Infiltration commonly begins in the perihilar region (where the bronchus begins) and spreads in a wedge- or fan-shaped fashion toward the periphery of the lung field. The process most often involves the lower lobe but may affect any lobe or combination of lobes.[5]
Epidemiology
Mycoplasma is found more often in younger than in older people.[16][17] Older people are more often infected by Legionella.[17]
Terminology
"Primary atypical pneumonia" is called primary because it develops independently of other diseases.[citation needed]
It is commonly known as "walking pneumonia" because its symptoms are often mild enough that one can still be up and about.[18][19]
"Atypical pneumonia" is atypical in that it is caused by atypical organisms (other than Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis).[20] These atypical organisms include special
At the time that atypical pneumonia was first described, organisms like Mycoplasma, Chlamydophila, and Legionella were not yet recognized as bacteria and instead considered viruses. Hence "atypical pneumonia" was also called "non-bacterial".[21]
In literature the term atypical pneumonia is current, sometimes contrasted with viral pneumonia (see below) and sometimes, though incorrectly, with bacterial pneumonia. Many of the organisms causative of atypical pneumonia are unusual types of bacteria (Mycoplasma is a type of bacteria without a cell wall and Chlamydias are intracellular bacteria). As the conditions caused by the various agents have different courses and respond to different treatments, the identification of the specific causative pathogen is important.[citation needed]
References
- ^ "Atypical Pneumonia (Walking Pneumonia)". Cleveland Clinic.
- ^ S2CID 5232855.
- ^ Pneumonia, Atypical Bacterial at eMedicine
- ^ Pneumonia, Typical Bacterial at eMedicine
- ^ PMID 18015969.
- S2CID 8918777.
- PMID 10983928.
- ^ PMID 16669925.
- ^ Robbins and Cotran Pathologic Basis of Disease, 8th edition, Kumar et al., Philadelphia, 2010, p. 714
- ^ "Atypical pneumonia may be caused by or feature of (sorted by category) Diseases Database". www.diseasesdatabase.com.
- PMID 14653964. Archived from the original(PDF) on 2011-07-08.
- ^ "Severe Acute Respiratory Syndrome (SARS) – multi-country outbreak". Archived from the original on 7 December 2008. Retrieved 2008-12-21.
- ^ a b Diseases Database Causes of atypical pneumonia
- PMID 17242382.
- S2CID 10894988.
- PMID 15198183.
- ^ a b "Pneumonia". National Heart, Lung and Blood Institute. 24 March 2022.
- ^ Association, American Lung. "What Is Walking Pneumonia?". www.lung.org.
- ^ "What is walking pneumonia? How does it differ from more serious pneumonia?". Mayo Clinic.
- S2CID 37758739.
- ^ "Primary atypical pneumonia" at Dorland's Medical Dictionary