Study on pleural effusions due to Mycoplasma pneumoniae infection

Objectives To find the incidence of pleural effusions among patients with Mycoplasma pneumoniae pneumonia. Design Prospective study Setting University paediatric unit, Karapitiya, Galle. Method Patients with pneumonia admitted to university paediatric unit from November 1998 to October 1999 were included. Pleural effusions were confirmed either radiologically or by ultrasound examination. Large pleural effusions causing respiratory distress or persistent effusions were aspirated. Results There were 133 patients with pneumonia. 24 children (14 boys, 10 girls) had Mycoplasma pneumoniae pneumonia. All but one were above 4 years of age. Four of the 24 children had pleural effusions. Two effusions were aspirated and were found to be exudates. Conclusions Mycoplasma pneumoniae should be considered an aetological agent in pleural effusions especially when associated with lobar pneumonia


Introduction
Mycoplasma pneumoniae is a common aetio-logical agent of community-acquired pneumonia in both children and adults 1,2 .It can cause a wide variety of respiratory tract manifestations including acute pharyngitis, bronchitis, bronchiolitis and bronchopneumonia.Pneumonia due to Mycoplasma pneumoniae is commonly a mild bronchopneumonia or interstitial pneumonia not requiring hospital admission.Severe lobar pneumonia, lung abscess and pleural effusions are uncommon manifestations 3 .
Adult respiratory distress syndrome is a rare complication of this infection4.Pleural effusion is also a recognized manifestation.____________________________________ Senior Lecturer, Department of Paediatricsm Faculty of Medicine, Galle.

(Received on 12 May 2004)
According to Juang et al pleural effusion due to Mycoplasma pneumoniae pneumonia is 24% 5 .Confluent consolidation without typical lobar pneumonia was seen in 56% of patients.Mycoplasma pneumoniae could be isolated from the pleural fluid in some patients with Mycoplasma pneumoniae pneumonia 6 .In most instances pleural effusions are self-limiting and recover with antimycoplasma therapy.

Method
Patients with pneumonia admitted to university paediatric unit from November 1998 to October 1999 were included.Mycoplasma antibody titres were performed in all the patients with pneumonia by using particle agglutination test, in addition to the conventional tests such as full blood count, chest x-ray etc.All patients with serologically proven Mycoplasma pneumoniae pneumonia were examined for the presence of pleural effusions.Pleural effusion was confirmed radiologically and by ultrasound examination.Consent was obtained from parents.Ethical approval for the study was obtained from the Ethics Committee of the Faculty of Medicine.Mycoplasma serology was tested by particle agglutination test done at Micro-biology Department, Faculty of Medicine, Galle.

Results
There were 133 patients with pneumonia seen from November 1998 to October 1999.105 patients had lobar pneumonia, 28 patients had interstitial and/or bronchopneumonia.19 patients (11 boys, 8 girls) with lobar pneumonia were due to Mycoplasma pneumoniae.Mycoplasma antibody titres ranged from 640-20,480.18 of them were above 4 years.4 of the 19 had pleural effusions (Figure 1).Pleural fluid aspiration was done in 2 patients.Analysis of pleural fluid showed presence of exudates (table 1). 3 effusions were diagnosed radiologically and one mild effusion was diagnosed by ultrasound examination.5 children (3 boys, 2 girls) with interstitial pneumonia had Mycoplasma pneumoniae aetiology.None of them had pleural effusions.

Discussion
Mycoplasma pneumoniae is a common aetiological agent in childhood pneumonia.According to Albeit et al Mycoplasma pneumoniae pleural effusions are uncommon and tend to occur with a severe illness 6 .In most instances pleural effusions are mild and resolve with the antimycoplasmal therapy.It can rarely lead to respiratory distress requiring aspiration of pleural fluid.In our study 4 (16%) out of 24 patients with Mycoplasma pneumoniae pneumonia had pleural effusions.Pleural fluid, aspirated in 2 patients due to respiratory distress and persistent fever, showed the presence of an exudate.High protein content and the presence of inflammatory cells (polymorphs and lymphocytes) were seen in both samples of pleural fluid.Subsequent follow up of these patients with pleural effusions was uneventful.According to some studies Mycoplasma pneumoniae had been isolated from the pleural fluid 7 .Study by Nagayama et al found 56 patients with Mycoplasma pneumoniae pleural effusions among 773 patients with Mycoplasma pneumoniae infection 8 .Polymerase chain reaction (PCR) seems to be the best way to diagnose Mycoplasma pneumoniae pleural effusions 9 .In the absence of this facility,diagnosis of Mycoplasma pneumoniae pleural effusion could be made in the presence of high Mycoplasma antibody titre in association with synpneumonic pleural effusion.Microparticle agglutination test is a highly specific and sensitive serological test 10 .

Conclusions
Syn-pneumonic pleural effusions are commonly seen with bacterial pneumonia.According to the results of this study about 16% of Mycoplasma lobar pneumonia patients had syn-pneumonic effusions.Therefore Mycoplasma pneumoniae has to be considered an aetiological agent in children with pleural effusions especially when associated with lobar pneumonia.

Table 1
Analysis of pleural fluid in patients with Mycoplasma pneumoniae pneumonia