| ICDO | OMIM | MedlinePlus 000079 | eMedicineSubj | eMedicineTopic | MeshID }} Atypical pneumonia is a pneumonia not caused by one of the more traditional pathogens. It can be caused by a variety of microorganism . When developed independently from another disease it is called Primary Atypical Pneumonia (PAP). The term was introduced in the 1930s C. Walter, M.D. McCoy http://scholar.google.com/scholar?qinfo:B1yIRrr44H0J:scholar.google.com/&outputviewport Primary atypical pneumonia*A report of 420 cases with one fatality during twenty-seven month at Station Hospital, Camp Rucker, Alabama]; Southern Medical Journal, 1946 39(9): 696 lt;/ref> and was contrasted with the bacterial pneumonia caused by [[Streptococcus pneumoniae]] at that time the best known and most 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 and myalgia and bronchopneumonia lt;ref>eMedicine article 360090: Pneumonia, Typical Bacterial. Distinction between atypical and typical pneumonia, however, is medically insufficient. For the treatment of pneumonia it is important to know the exact causal organism. Moreover, S. pneumoniaehas become a relatively lesser important cause.

Terminology

"Primary atypical pneumonia" is called primaryto indicate, that it developed independently, not following another disease.
"Atypical pneumonia" is atypicalin that it is caused by atypical organisms (other than [[Streptococcus pneumoniae]] [[Haemophilus influenzae]]and [[Moraxella catarrhalis]]. lt;/ref> These atypical organisms include special bacteria viruses fungi and protozoa Diseases Database http://www.diseasesdatabase.com/result.asp?glngUserChoice1132&bytRel2&blnBW0&strBBRL&blnClassSort255 Causes of atypical pneumonia At the time that atypical pneumonia was described first, organisms like Mycoplasma, Chlamydophila and Legionella still were not recognized as bacteria and instead considered as viruses. Hence "atypical pneumonia" was also called "non-bacterial". lt;/ref> In literature the term bacterial pneumoniacontrasted with atypical pneumoniais, although actually incorrect, still in use. Meanwhile, many of such organisms are identified as bacteria, albeit unusual types (Mycoplasmais a type of bacteria without a cell wall and Chlamydiasare intracellular parasites). As the conditions caused by these agents have different courses and respond to different treatments, the identification of the specific causative pathogen is important.

Signs and symptoms

Usually the atypical causes also involve atypical symptoms: *No responding on common antibiotics as Sulfonamide (medicine) lt;ref namebragg/> and Beta-lactam antibiotic like penicillin *No signs and symptoms of lobar consolidationlt;/ref>lt;/ref>, 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 *Extrapulmonary symptoms, related to the causing organism.lt;/ref> *Moderate amount of sputum. *Lack of alveolar exudate.p714, Robbins and Cotran Pathologic Basis of Disease8th edition, Kumar et al, Philadelphia 2010 *Despite general symptom and problems with the upper respiratory tract like high fever, headache, a dry irritating cough, later a productive cough and radiographs, showing Consolidation (medicine) there are in general few physical signs. The patient looks worse than the symptoms suggest.

Cause

The most common causative organisms are (often intracellular parasite living) bacteria: lt;/ref> ;Chlamydophila pneumoniae Mild form of pneumonia with relatively mild symptoms. ;Chlamydophila 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 lt;ref>lt;/ref>: Usually occurs in younger age groups and may be associated with neurological and systemic (e.g. rashes) symptoms. Atypical pneumonia can also have a fungal, protozoan or viral cause.http://www.diseasesdatabase.com/result.asp?glngUserChoice1132&bytRel2&blnBW0&strBBRL&blnClassSort255 Diseases Database] lt;/ref>
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.

Viral

When comparing the bacterial-caused atypical pneumonias with these caused by real viruses (excluding bacteria that were wrongly considered as viruses), the term "atypical pneumonia" almost always implies a bacterial etiologyand is contrasted with viral pneumonia Known viral causes of atypical pneumonia are severe acute respiratory syndrome (SARS) lt;/ref> and measles

Diagnosis

Chest radiograph (X-ray photographs) often show a pulmonary affection before physical signs of atypical pneumonia are observable at all. This is called 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. C.G. Murphy et al. http://www.futuremedicine.com/doi/full/10.2217/14750708.5.4.399 Clinical predictors of occult pneumonia in the febrile child. Acad. Emerg. Med. 14(3), 243–249 (2007). lt;/ref> Infiltration (medical) 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. Commission on Acute Respiratory Diseases, Fort Bragg, North Carolina http://www.ajph.org/cgi/reprint/34/4/347.pdf Primary Atypical Pneumonia] American J. of Public Health, April, 1944; Vol. 34

Epidemiology

Mycoplasma is found more often in younger than in elder people. lt;/ref> National Heart, Lung, and Blood Institute, U.S.A. http://www.nhlbi.nih.gov/health/dci/Diseases/pnu/pnu_causes.html What Causes Pneumonia? Elder people are more often infected by Legionella.

External links

*Phyllis C. Braun, PhD, and John D. Zoidis, MD http://www.rtmagazine.com/issues/articles/2004-09_03.asp Atypical Pneumonia September 2004 * Norman L. Cressy, M.D. http://history.amedd.army.mil/booksdocs/wwii/PM4/CH12.Pneumonia.htm The Pneumonias (From: http://history.amedd.army.mil/booksdocs/wwii/PM4/PM4default.htm Preventive Medicine in World War II Series], Volume IV: Communicable Diseases: Transmitted Chiefly through Respiratory and Alimentary Tracts, Chapter XII) *http://jac.oxfordjournals.org/cgi/pmidlookup?viewlong&pmid9145823.pdf Atypical pneumonia in the Nordic countries: aetiology and clinical results of a trial comparing fleroxacin and doxycycline.] pmid 9145823; journalJ. Antimicrob. Chemother. , volume39, pages499–508 year1997 *The difference between M. pneumoniaeand S. pneumoniaeon high-resolution-CT http://www.pubmedcentral.nih.gov/articlerender.fcgi?toolpubmed&pubmedid19400968 BMC Med Imaging. 2009]

References

Category:Pneumonia ca:Pneumònia atípica da:Atypisk pneumoni es:Neumonía atípica wuu:非典型性肺炎 zh:非典型肺炎