Legionnaires' disease. Clinical and pulmonary histopathologic features of a sporadic case.

The pulmonary histopathologic features in a sporadic case of Legionnaires' disease are shown. The changes include acute bronchitis with focal ulceration and diffuse acute interstitial pneumonitis. These changes are not those seen with typical bacterial pneumonia but are similar to changes seen when viruses, rickettsiae, chlamydiae, or Mycoplasma pneumoniae organisms are the infecting agents.