Radiographic features of Mycoplasma pneumoniae pneumonia: differential diagnosis and performance timing

The Japanese Respiratory Society guidelines propose a differential diagnosis for atypical pneumonia and bacterial pneumonia using a scoring system for the selection of appropriate antibiotic. In order to improve this scoring system, the guidelines are seeking new specific parameter. The purpose of this study was to clarify the pattern of abnormalities with Mycoplasma pneumoniae pneumonia on chest computed tomography (CT) and whether the radiographic findings could distinguish M. pneumoniae pneumonia from Streptococcus pneumoniae pneumonia.

A retrospective review was performed of the CT findings of 64 cases and 68 cases where M. pneumoniae and S. pneumoniae, respectively, were the only pathogen identified by the panel of diagnostic tests used.

Of the 64 patients with M. pneumoniae pneumonia, bronchial wall thickening was observed most frequently (81%), followed by centrilobular nodules (78%), ground-glass attenuation (78%), and consolidation (61%). Bronchial wall thickening and centrilobular nodules were observed more often in M. pneumoniae patients than in S. pneumoniae patients (p < 0.0001). The presence of bilateral bronchial wall thickening or centrilobular nodules was only seen in patients with M. pneumoniae pneumonia. Using the scoring system of the Japanese Respiratory Society guidelines and chest CT findings, 97% of M. pneumoniae patients were suspected to be M. pneumoniae pneumonia without serology. When comparing the CT findings between early stage and progressed stage in the same patients with severe pneumonia, the radiographic features of early stage M. pneumoniae pneumonia were not observed clearly in the progressed stage.

The present results indicate that the diagnosis of M. pneumoniae pneumonia would appear to be reliable when found with a combination of bronchial wall thickening and centrilobular nodules in the CT findings. However, these CT findings are not observed in progressed severe M. pneumoniae pneumonia patients.