Studies of lung tissues and bronchoalveolar lavage specimens from pati
ents with pneumonia have led some investigators to propose that human
herpesvirus 6 (HHV-6) can cause pneumonia. As the etiologic role of HH
V-6 in pneumonia remains poorly defined, cases of pneumonia that are a
ssociated with pulmonary HHV-6 infection are best described as HHV-6-a
ssociated pneumonias. The clinical spectrum of HHV-6-associated pneumo
nia encompasses both mild and severe cases. Most cases reported so far
occurred in immunosuppressed individuals following bone marrow transp
lantation or HIV infection. Some studies have identified coinfections
with HHV-6 and other viruses in a surprising number of HHV-6-associate
d pneumonias. Although no systematic evaluation of treatment regimens
is available at this time, coincidental administration of antiviral dr
ugs did not generally result in clinical improvement. Controlled, pros
pective studies are needed to understand the clinical presentation, cl
inical course, etiology, diagnosis and treatment of HHV-6-associated p
neumonias.