mycoplasma pneumonia

Mycoplasma pneumonia is a type of community-acquired pneumonia caused by the organism Mycoplasma pneumoniae. It is usually grouped under atypical pneumonia.


It is relatively common in the pediatric population where it is considered the most common community-acquired pneumonia in 5 to 20-year-olds (may account for 40% of such cases ). It may account for 10-15% of community-acquired pneumonia in adults. In adults, mycoplasma can rarely result in bronchiolitis without giving pneumonia.


M. pneumoniae is the smallest organism which can be cultured in vitro and lacks a cell wall, hence it is resistant to the penicillins. It spreads via inhalation of aerosolized droplets containing the microorganisms. It initially involves the peribronchovascular interstitium and then extends to the adjacent alveoli.

Extrapulmonary manifestations:

Radiographic features

Plain radiograph

There can be variable chest radiographic features, although four different patterns have been described.  No pattern is, however, pathognomonic:

  • peribronchial and perivascular interstitial infiltrates - reticular densities most common ~49% (can be patchy with a segmental or non-segmental distribution)
  • airspace consolidation ~38%
  • reticulonodular opacification ~8%
  • nodular or mass-like opacification ~5%. 

Bilateral peribronchial perivascular interstitial infiltrates in central and middle lung zones have also been described. Lower lobes are most commonly involved.

Other reported plain film findings include bilateral lesions, pleural effusion (uncommon - in ~25% of cases) and hilar lymphadenopathy.


Areas of ground-glass attenuation and air-space consolidation have been reported as being frequent on HRCT (~80% of cases )

In about 60% of cases, areas of consolidation may have a lobular distribution evident on CT.

Intrapulmonary nodules can also be seen (~90% of cases) and these tend to have a predominantly centrilobular distribution .

Other findings include thickening of the bronchovascular bundles.

Treatment and prognosis

Most patients recover well although a small proportion of patients may develop bronchiectasis in the affected region or Swyer James syndrome.

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