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cases. Hypoxemia suggests a poor prognosis, and the overall mortality is about 40%. Treatment
with ganciclovir may be useful in the setting of a diffuse interstitial pneumonia with hypoxemia
and histologic evidence for CMV in the absence of other pathogens.[418,619]
Radiographic features of CMV pneumonia overlap those of other opportunistic infections
with AIDS such as PCP. These features may be present in two thirds of cases. There can be
ground glass opacifications, nodules ranging from miliary to 3 cm, perihilar and lower lung field
interstitial infiltrates, small airway disease, and pleural effusions.[607]
There are no specific gross pathologic changes attributable to CMV. The findings may
resemble PCP, though extrapulmonary disease more strongly suggests CMV. The distribution of
CMV in the lung may be alveolar, interstitial, or tracheobronchial. Characteristic inclusion
bodies are more often seen within epithelial cells of the lung. Occasionally, inclusions are seen
in vascular endothelium, more often in the tracheobronchial tree. The patterns of involvement
include focal interstitial pneumonitis and acute necrotizing tracheobronchitis, though vasculitis
may also be seen. More florid cases of CMV pneumonitis may present with areas of patchy to
confluent red or tan consolidation. This can progress to diffuse alveolar damage. Areas of
hemorrhage may be present.[619]
Microscopic presence of cytomegalic cells with intranuclear inclusions is necessary for
light microscopic diagnosis with hematoxylin-eosin staining. Inclusions may be scant to
numerous. Cytomegalic cells may line alveolar spaces, appear within the lumens of air spaces,
or involve endothelium. When CMV infection is florid, two or more inclusions may be seen
within a cytomegalic cell. Since inclusions may be difficult to find in tissue biopsy or cytologic
material, direct fluorescence antibody staining, culture, and use of immunohistochemistry or in
situ hybridization may be very helpful ancillary techniques. Accompanying inflammation may
not always be present, but in florid cases consists of many polymorphonuclear leukocytes and/or
lymphocytes. Inflammatory infiltrates are primarily within interstitium, but can be alveolar in
florid cases. A search should be made for additional opportunistic infectious agents, particularly
P jiroveci (carinii).[619]

CRYPTOCOCCAL PNEUMONITIS.-- Infection with Cryptococcus neoformans
probably occurs after inhalation of an aerosol containing the unencapsulated yeast, but there is
no known environmental factor that consistently increases the risk for infection. C neoformans
can be found throughout the world. Colonization of the tracheobronchial tree, followed by
pulmonary infection, whether silent or symptomatic, probably precedes dissemination to other
organs. There are no specific clinical signs or symptoms of cryptococcal pneumonia; patients
may have fever, night sweats, fatigue, and headache for days to months. About a third of
patients with cryptococcosis have respiratory symptoms including cough and dyspnea.
Diagnosis of disseminated cryptococcal infection can initially be made by the sensitive and
specific cryptococcal antigen test that can be run on serum, cerebrospinal fluid, or pleural fluid.
However, this antigen test may be negative with isolated pulmonary disease.[598,614]
Radiographic findings with cryptococcal pneumonia include patchy irregular or mass-like
airspace opacities as well as lobar or segmental consolidation, without a lobar predilection.
Nodules or masses are common, including tiny subpleural or peripheral interstitial nodules with
adjacent interstitial thickening or pleural thickening. Widespread interstitial disease and
effusions are not common. Lymphadenopathy is seen in more than a third of patients, is usually
not pronounced (<1.5 cm), and always present with other findings. A combination of findings is
more frequent than a single abnormality.[620]