An unusual case of lung abscess secondary to round pneumonia caused by recurrent Klebsiella pneumoniae strain and the role of occult metastases tumor

Shuchang An, Xiangli Li, Shenhai Wei, Chaofeng Luo, Rong Cui
An unusual case of lung abscess secondary to round pneumonia caused by recurrent Klebsiella pneumoniae strain and the role of occult metastases tumor
Respiratory Medicine Case Reports 2018 Volume 23, Pages 107–109

肺転移を伴った再発性の肺炎桿菌感染に起因する肺膿瘍を合併した77歳の男性1例の報告。円形肺炎は、通常は小児に見られる市中肺炎の珍しい形である。 成人患者のこのタイプの局所肺合併症に関する報告はない。潜在性転移が空洞形成に重要な役割を果たした可能性がある。 再発感染と転移との関係に関するさらなる調査が必要である。


疑問点　
1)この画像を円形肺炎としてよいのかという定義があいまい。
2)この肺病変の中に転移が存在していたとする証拠がない。
潜在性転移（あるいは癌）による気道のドレナージ障害により閉鎖領域における緊満形状の肺炎が反復して起こりうる という点は理解できる。

Round pneumonia
Round pneumonia is a type of pneumonia usually only seen in paediatric patients. They are well defined, rounded opacities that represent regions of infected consolidation.
1.Epidemiology
The mean age of patients with round pneumonia is 5 years and 90% of patients who present with round pneumonia are younger than twelve 5. Rounded pneumonia is uncommon after the age of eight because collateral airways tend to be well developed by this age.
2.Clinical presentation
Presentation is with symptoms of chest infection and therefore, with symptoms such as fever, sweats and cough. Most of the children who present to Emergency with chest complaints have these symptoms, so they are unhelpful in modification of pre-test probability. However, history of these symptoms is really helpful when excluding other differentials.
3.Pathology
The proposed theory about why children develop round pneumonia and adults do not relates to the development of inter-alveolar communication and collateral airways. These are called pores of Kohn and canals of Lambert and when they develop, they allow air-drift between the parenchymal subsegments. In adults, these allow lateral dissemination of infection throughout a lobe, leading to lobar pneumonia. In children, where these have not developed, the limited spread of infection results in round pneumonia.
The infective agent in round pneumonia is bacterial. There is no specific bacterium that causes round pneumonia, but since Streptococcus pneumoniae is the most common cause of chest infection, it is little surprise that it is the leading cause of round pneumonia.
(Radiopedia:Dr Pir Abdul Ahad Aziz and Dr Yuranga Weerakkody  et al.)