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Atypical pneumonia, also known as walking pneumonia, is the type of pneumonia not caused by one of the more traditional pathogens. 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 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. Distinction between atypical and typical pneumonia, however, is medically insufficient. For the treatment of pneumonia it is important to know the exact causal organism. ==Terminology== "Primary atypical pneumonia" is called ''primary'' because it develops independently of other diseases. "Atypical pneumonia" is ''atypical'' in that it is caused by atypical organisms (other than ''Streptococcus pneumoniae'', ''Haemophilus influenzae'', and ''Moraxella catarrhalis''). 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.〔Diseases Database (''Causes of atypical pneumonia'' )〕〔 At the time that atypical pneumonia was first described, organisms like Mycoplasma, Chlamydophila, and Legionella still were not recognized as bacteria and instead considered viruses. Hence "atypical pneumonia" was also called "non-bacterial". In literature the term ''atypical pneumonia'' (contrasted with ''bacterial pneumonia'') is still in use, though incorrect. Meanwhile, many such organisms are identified as bacteria, albeit unusual types (''Mycoplasma'' is a type of bacteria without a cell wall and ''Chlamydias'' are 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Atypical pneumonia」の詳細全文を読む スポンサード リンク
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