Atypical pneumonia

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Atypical pneumonia
Other namesWalking pneumonia
Specialty 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).

Contents

The term was introduced in the 1930s [2] [3] and was contrasted with the bacterial pneumonia caused by Streptococcus pneumoniae , at that time the best known and most commonly occurring form of pneumonia. The distinction was historically considered important, as it differentiated those more likely to present with "typical" respiratory symptoms and lobar pneumonia from those more likely to present with "atypical" generalized symptoms (such as fever, headache, sweating and myalgia) and bronchopneumonia. [4]

Signs and symptoms

Usually, the atypical causes also involve atypical symptoms:

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 legionellosis or 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 respiratory syncytial virus (RSV), influenza A and B, parainfluenza, adenovirus, severe acute respiratory syndrome (SARS), [12] Middle East respiratory syndrome (MERS), and measles. [13]

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 bacteria, viruses, fungi, and protozoa. In addition, this form of pneumonia is atypical in presentation with only moderate amounts of sputum, no consolidation, only small increases in white cell counts, and no alveolar exudate. [13] [8]

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 above) 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 ]

Related Research Articles

<span class="mw-page-title-main">Pneumonia</span> Inflammation of the alveoli of the lungs

Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity of the condition is variable.

<span class="mw-page-title-main">Sputum</span> Mucus that is coughed up from the lower airways

Sputum is mucus that is coughed up from the lower airways. In medicine, sputum samples are usually used for a naked eye examination, microbiological investigation of respiratory infections and cytological investigations of respiratory systems.

<span class="mw-page-title-main">Acute bronchitis</span> Medical condition

Acute bronchitis, also known as a chest cold, is short-term bronchitis – inflammation of the bronchi of the lungs. The most common symptom is a cough. Other symptoms include coughing up mucus, wheezing, shortness of breath, fever, and chest discomfort. The infection may last from a few to ten days. The cough may persist for several weeks afterward with the total duration of symptoms usually around three weeks. Some have symptoms for up to six weeks.

Mycoplasma pneumoniae is a species of very small-cell bacteria that lack a cell wall, in the class Mollicutes. M. pneumoniae is a human pathogen that causes the disease Mycoplasma pneumonia, a form of atypical bacterial pneumonia related to cold agglutinin disease.

<i>Streptococcus pneumoniae</i> Species of bacterium

Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic member of the genus Streptococcus. S. pneumoniae cells are usually found in pairs (diplococci) and do not form spores and are non motile. As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.

<span class="mw-page-title-main">Lower respiratory tract infection</span> Medical term

Lower respiratory tract infection (LRTI) is a term often used as a synonym for pneumonia but can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue. A routine chest X-ray is not always necessary for people who have symptoms of a lower respiratory tract infection.

<span class="mw-page-title-main">Bacterial pneumonia</span> Disease of the lungs

Bacterial pneumonia is a type of pneumonia caused by bacterial infection.

Mycoplasma pneumonia is a form of bacterial pneumonia caused by the bacterium Mycoplasma pneumoniae.

<i>Chlamydia pneumoniae</i> Species of bacterium

Chlamydia pneumoniae is a species of Chlamydia, an obligate intracellular bacterium that infects humans and is a major cause of pneumonia. It was known as the Taiwan acute respiratory agent (TWAR) from the names of the two original isolates – Taiwan (TW-183) and an acute respiratory isolate designated AR-39. Briefly, it was known as Chlamydophila pneumoniae, and that name is used as an alternate in some sources. In some cases, to avoid confusion, both names are given.

Community-acquired pneumonia (CAP) refers to pneumonia contracted by a person outside of the healthcare system. In contrast, hospital-acquired pneumonia (HAP) is seen in patients who have recently visited a hospital or who live in long-term care facilities. CAP is common, affecting people of all ages, and its symptoms occur as a result of oxygen-absorbing areas of the lung (alveoli) filling with fluid. This inhibits lung function, causing dyspnea, fever, chest pains and cough.

<span class="mw-page-title-main">Lobar pneumonia</span> Medical condition

Lobar pneumonia is a form of pneumonia characterized by inflammatory exudate within the intra-alveolar space resulting in consolidation that affects a large and continuous area of the lobe of a lung.

<span class="mw-page-title-main">Sputum culture</span> Medical test to detect & identify bacteria or fungi in lung airways

A sputum culture is a test to detect and identify bacteria or fungi that infect the lungs or breathing passages. Sputum is a thick fluid produced in the lungs and in the adjacent airways. Normally, fresh morning sample is preferred for the bacteriological examination of sputum. A sample of sputum is collected in a sterile, wide-mouthed, dry, leak-proof and break-resistant plastic-container and sent to the laboratory for testing. Sampling may be performed by sputum being expectorated, induced, or taken via an endotracheal tube with a protected specimen brush in an intensive care setting. For selected organisms such as Cytomegalovirus or "Pneumocystis jiroveci" in specific clinical settings a bronchoalveolar lavage might be taken by an experienced pneumologist. If no bacteria or fungi grow, the culture is negative. If organisms that can cause the infection grow, the culture is positive. The type of bacterium or fungus is identified by microscopy, colony morphology and biochemical tests of bacterial growth.

Pneumococcal pneumonia is a type of bacterial pneumonia that is caused by Streptococcus pneumoniae (pneumococcus). It is the most common bacterial pneumonia found in adults, the most common type of community-acquired pneumonia, and one of the common types of pneumococcal infection. The estimated number of Americans with pneumococcal pneumonia is 900,000 annually, with almost 400,000 cases hospitalized and fatalities accounting for 5-7% of these cases.

Chlamydia felis is a Gram-negative, obligate intracellular bacterial pathogen that infects cats. It is endemic among domestic cats worldwide, primarily causing inflammation of feline conjunctiva, rhinitis and respiratory problems. C. felis can be recovered from the stomach and reproductive tract. Zoonotic infection of humans with C. felis has been reported. Strains FP Pring and FP Cello have an extrachromosomal plasmid, whereas the FP Baker strain does not. FP Cello produces lethal disease in mice, whereas the FP Baker does not. An attenuated FP Baker strain, and an attenuated 905 strain, are used as live vaccines for cats.

<span class="mw-page-title-main">Hospital-acquired pneumonia</span> Pneumonia contracted by a hospital patient

Hospital-acquired pneumonia (HAP) or nosocomial pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. It is thus distinguished from community-acquired pneumonia. It is usually caused by a bacterial infection, rather than a virus.

<span class="mw-page-title-main">Pathogenic bacteria</span> Disease-causing bacteria

Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. By contrast, several thousand species are part of the gut flora present in the digestive tract.

<span class="mw-page-title-main">Acute exacerbation of chronic obstructive pulmonary disease</span> Medical condition

An acute exacerbation of chronic obstructive pulmonary disease, or acute exacerbations of chronic bronchitis (AECB), is a sudden worsening of chronic obstructive pulmonary disease (COPD) symptoms including shortness of breath, quantity and color of phlegm that typically lasts for several days.

Atypical bacteria are bacteria that do not get colored by gram-staining but rather remain colorless: they are neither Gram-positive nor Gram-negative. These include the Chlamydiaceae, Legionella and the Mycoplasmataceae ; the Spirochetes and Rickettsiaceae are also often considered atypical.

<span class="mw-page-title-main">Classification of pneumonia</span> Medical condition

Pneumonia can be classified in several ways, most commonly by where it was acquired, but may also by the area of lung affected or by the causative organism. There is also a combined clinical classification, which combines factors such as age, risk factors for certain microorganisms, the presence of underlying lung disease or systemic disease and whether the person has recently been hospitalized.

Necrotizing pneumonia (NP), also known as cavitary pneumonia or cavitatory necrosis, is a rare but severe complication of lung parenchymal infection. In necrotizing pneumonia, there is a substantial liquefaction following death of the lung tissue, which may lead to gangrene formation in the lung. In most cases patients with NP have fever, cough and bad breath, and those with more indolent infections have weight loss. Often patients clinically present with acute respiratory failure. The most common pathogens responsible for NP are Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae. Diagnosis is usually done by chest imaging, e.g. chest X-ray or CT scan. Among these, a CT scan is the most sensitive test, which shows loss of lung architecture and multiple small thin walled cavities. Often cultures from bronchoalveolar lavage and blood may be done for identification of the causative organism(s). It is primarily managed by supportive care along with appropriate antibiotics. However, if a patient develops severe complications like sepsis or fails to medical therapy, surgical resection is a reasonable option for saving life.

References

  1. ↑ "Atypical Pneumonia (Walking Pneumonia)". Cleveland Clinic.
  2. 1 2 Walter C, McCoy MD (1946). "Primary atypical pneumonia: A report of 420 cases with one fatality during twenty-seven month at Station Hospital, Camp Rucker, Alabama". Southern Medical Journal. 39 (9): 696–706. doi:10.1097/00007611-194609000-00005. PMID   20995425. S2CID   5232855.
  3. ↑ Pneumonia, Atypical Bacterial at eMedicine
  4. ↑ Pneumonia, Typical Bacterial at eMedicine
  5. 1 2 3 4 Commission on Acute Respiratory Diseases, Fort Bragg, North Carolina (April 1944). "Primary Atypical Pneumonia". American Journal of Public Health and the Nation's Health. 34 (4): 347–57. doi:10.2105/AJPH.34.4.347. PMC   1625001 . PMID   18015969.
  6. ↑ Gouriet F, Drancourt M, Raoult D (October 2006). "Multiplexed serology in atypical bacterial pneumonia". Ann. N. Y. Acad. Sci. 1078 (1): 530–40. Bibcode:2006NYASA1078..530G. doi:10.1196/annals.1374.104. PMID   17114771. S2CID   8918777.
  7. ↑ Hindiyeh M, Carroll KC (June 2000). "Laboratory diagnosis of atypical pneumonia". Semin Respir Infect. 15 (2): 101–13. doi:10.1053/srin.2000.9592. PMID   10983928.
  8. 1 2 3 Cunha BA (May 2006). "The atypical pneumonias: clinical diagnosis and importance". Clin. Microbiol. Infect. 12 (Suppl 3): 12–24. doi:10.1111/j.1469-0691.2006.01393.x. PMC   7128183 . PMID   16669925.
  9. ↑ Robbins and Cotran Pathologic Basis of Disease, 8th edition, Kumar et al., Philadelphia, 2010, p. 714
  10. ↑ "Atypical pneumonia may be caused by or feature of (sorted by category) Diseases Database". www.diseasesdatabase.com.
  11. ↑ Tang YW (December 2003). "Molecular diagnostics of atypical pneumonia" (PDF). Acta Pharmacol. Sin. 24 (12): 1308–13. PMID   14653964. Archived from the original (PDF) on 2011-07-08.
  12. ↑ "Severe Acute Respiratory Syndrome (SARS) – multi-country outbreak". Archived from the original on 7 December 2008. Retrieved 2008-12-21.
  13. 1 2 Diseases Database Causes of atypical pneumonia
  14. ↑ Murphy CG, van de Pol AC, Harper MB, Bachur RG (March 2007). "Clinical predictors of occult pneumonia in the febrile child". Acad Emerg Med. 14 (3): 243–49. doi: 10.1197/j.aem.2006.08.022 . PMID   17242382.
  15. ↑ Rutman MS, Bachur R, Harper MB (January 2009). "Radiographic pneumonia in young, highly febrile children with leukocytosis before and after universal conjugate pneumococcal vaccination". Pediatric Emergency Care. 25 (1): 1–7. doi:10.1097/PEC.0b013e318191dab2. PMID   19116501. S2CID   10894988.
  16. ↑ Schneeberger PM, Dorigo-Zetsma JW, van der Zee A, van Bon M, van Opstal JL (2004). "Diagnosis of atypical pathogens in patients hospitalized with community-acquired respiratory infection". Scand. J. Infect. Dis. 36 (4): 269–73. doi:10.1080/00365540410020127. PMID   15198183.
  17. 1 2 "Pneumonia". National Heart, Lung and Blood Institute. 24 March 2022.
  18. ↑ Association, American Lung. "What Is Walking Pneumonia?". www.lung.org.
  19. ↑ "What is walking pneumonia? How does it differ from more serious pneumonia?". Mayo Clinic.
  20. ↑ Memish ZA, Ahmed QA, Arabi YM, Shibl AM, Niederman MS (October 2007). "Microbiology of community-acquired pneumonia in the Gulf Corporation Council states". J Chemother. 19 (Suppl 1): 17–23. doi:10.1080/1120009x.2007.11782430. PMID   18073166. S2CID   37758739.
  21. ↑ "Primary atypical pneumonia" at Dorland's Medical Dictionary
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