Herpes simplex virus infection of the adult lower respiratory tract.

We have reported six adult patients with HSV infection of the lower respiratory tract diagnosed ante-mortem, and have reviewed the literature on this subject. An attempt has been made to define the natural history of the infection, and suggestions have been made regarding diagnosis and treatment. HSV can infect the lower respiratory tract in immunologically normal patients, as well as the immunocompromised host. Many patients have been burned, or intubated, or have other reasons for squamous metaplasia of the respiratory epithelium. The pathogenesis in many cases is an extension or aspiration of oropharyngeal HSV, but there is a suggestion that some cases may be hematogenously spread. The diagnosis of the site and presence of HSV infection should be based initially on cytologic findings, histologic findings, or both. Viral cultures or immunofluorescent or immunoperoxidase labeling can be used to confirm the cytologic and histologic diagnoses. Bronchoscopy is valuable for visualizing ulcerations or membranes in the respiratory tract, and for improving the sensitivity and specificity of the cytologic diagnosis. Because the process is most often focused in the tracheobronchial tree, percutaneous needle biopsy and open lung biopsy may be less sensitive than bronchoscopy. Standard serologic tests are, in general, not helpful diagnostically. They can help verify that a recent HSV infection has occurred, but do not differentiate between primary and recurrent infection, and do not help in localizing the site of infection. However, paired complement fixation or neutralizing antibody titers may be useful prognostically. If the titers do not rise in the presence of a documented HSV lower respiratory tract infection, the outcome is more likely to be fatal. The respiratory epithelium from the oral mucosa to the alveoli can be infected with HSV. The manifestations can range from a few scattered ulcers in the trachea to a severe ulcerative process resulting in an obstructing, inflammatory tracheobronchial membrane. Focal or diffuse pneumonia can also occur. No specific treatment for the illness can be recommended at this time. There is no evidence that currently available antiviral therapy is effective. The outcome of the illness seems to be largely dependent on the immunologic status of the host, complicating superinfections, and the progression of the underlying disease.