Patterns of measles pneumonitis

As a result of the enlarging pool of unvaccinated children and young adults, there has been an increase in serious measles pneumonitis in our areas. We recently examined autopsy and/or lung biopsy material from five children with fatal measles pneumonitis. Two patients were immunocompromised because of either prematurity or acute leukemia and died 13-16 days following onset of symptoms. Both had classic giant cell pneumonitis, with readily demonstrable intranuclear inclusions. Three other children without known immunocompromise had a more prolonged course. The lungs of these patients lacked the classic pattern and displayed instead a spectrum of less specific findings ranging from organizing diffuse alveolar damage to interstitial pneumonia with giant cells, but without viral inclusions. An accompanying necrotizing bronchiolitis was also present. Electron microscopy and/or detection of elevated measles-specific immunoglobulin M was necessary to confirm the diagnosis in these apparently immunocompetent patients. We conclude that the histologic features of fatal or serious measles pneumonitis are variable and depend to some extent on the immunocompetence of the host as well as the duration and tempo of the disease. Ancillary studies may be necessary to establish the diagnosis in cases lacking classic histopathologic features.