Mycoplasma and Viral Pneumonia

Mycoplasma pneumoniae and viruses remain among the most common causes of community acquired pneumonia (CAP), and account for approximately 30% or more of all cases. M. pneumoniae is a bacterium that lacks a cell wall, which results in certain microbiologic features absent in other bacteria. The combination of centrilobular nodules, peribronchial thickening and lobular ground-glass attenuation on CT is the most suggestive pattern identified in patients with M. pneumoniae pneumonia. Although cellular bronchiolitis is a non-specific finding, a patchy or clustered distribution should raise the possibility of infectious etiology, with the most likely causative agents being M. pneumoniae, tuberculosis and viral bronchiolitis. The radiologic findings of adult viral and M. pneumoniae pneumonias are variable and depend on the host and the virulence of the pathogen. The imaging findings in this chapter overlap with those found in in pneumonias caused by atypical microorganisms (e.g. virus, PCP pneumonia, etc.). CT imaging of immunocompetent patients with suspected viral or mycoplasma pneumonia is not indicated unless there is suspicion of complications. CT may be performed in patients with normal, equivocal, or nonspecific radiographic findings. Conversely, CT is often indicated in immunocompromised patients with a normal chest radiograph and suspected pulmonary infection.