Overview.
Herpes simplex virus pneumonia is a pneumonia caused by herpes simplex virus (HSV) infection.HSV infection often occurs in the upper respiratory tract and is rare in the lower respiratory tract. Herpes simplex virus pneumonia is seen in immunocompromised patients, patients with alcoholism, patients with burns, and most patients are adults.
Etiology
Caused by HSV infection, an important respiratory infectious agent. Restricted herpes simplex virus pneumonia arises from direct dissemination of the virus from the upper and lower respiratory tracts, whereas diffuse herpes simplex virus pneumonia is caused by virus that has diffused from genital or oral lesions (most likely hematogenous).
Symptoms.
Cough, shortness of breath, fever (>38.5°C), decreased white blood cell count, lung rales, hypoxemia, respiratory insufficiency, azotemia, common initial symptoms of shortness of breath and cough; HSV pneumonia may be accompanied by cutaneous mucosal HSV lesions that appear earlier than the pneumonia, and may be accompanied by diffuse fungal, cytomegalovirus, or bacterial infections; herpes simplex viral tracheitis, bronchiolitis, which may manifest as conventional treatment-naïve bronchospasm or stenosis; patients may have no chronic lung disease and no immunosuppressive disorders, which can sometimes lead to acute respiratory failure.
Examination
1. Serologic examination
The greatest value of this method is to prove that the patient has been infected with HSV. Anti-HSV antibodies in the blood circulation are a sign of the possibility of recurrent infection, and a 4-fold or greater increase in antibody titer suggests recent infection with HSV.
2. Histologic examination
Isolation of the virus directly from the lower respiratory tract, preferably from lung tissue, is of definite diagnostic significance.
3. Fiberoptic bronchoscopy
Shows tracheobronchial mucosal ulceration and/or covered with pseudomembrane.
4. Cytology and histology
Provides specific evidence of HSV infection with multinucleated giant cells and intranuclear eosinophilic inclusion bodies.
5. Biopsy specimen examination
Demonstrates inflammatory infiltrate, parenchymal necrosis and hemorrhage.
Diagnosis
The diagnosis of herpes simplex virus pneumonia must rely on the histologic basis of HSV lung infection and direct isolation of the virus from the lower respiratory tract (preferably from lung tissue), in addition to the clinical manifestations of pneumonia, for a definitive diagnosis. In addition, tracheoscopy combined with cytologic examination and viral culture has diagnostic significance.
Treatment
1. Acyclovir
Acyclovir is a drug used to treat HSV infection. Acyclovir is well tolerated for intravenous use, but can cause localized pain and phlebitis. Topical use is limited to the skin (e.g., lips, face, external genitalia) and should not be used on mucosal surfaces. The drug may also be associated with neurotoxicity, including drowsiness, tremor, delirium, and EEG abnormalities. Neurotoxicity of acyclovir is often predicted by resting or intentional tremor. Toxicity can be avoided by hydration with 800 to 1000 ml of fluid per gram of acyclovir. It should be given intravenously in patients with severe initial infections. Acyclovir is used orally in less severe cases and for treatment and suppression of recurrence in some ambulatory patients. In many patients with recalcitrant HSV infections, prolonged acyclovir dosing, higher doses, or continuous IV infusion can be successful. In severely immunocompromised patients with persistent and progressive HSV infection despite acyclovir therapy, which can progress to the viscera, a change in therapy must be considered, and drug susceptibility testing for HSV isolates must be performed to rationalize the choice of antiviral agents.
2.Trisodium phosphocarboxylate
Inhibits viral DNA polymerase, which does not require phosphorylation for activation. It may be better than adenosine in the treatment of drug-resistant HSV.
3. Adenosine
Activated by cytosolic enzymes rather than viral TK phosphorylation, it is effective against HSV cutaneous mucosal infections in immunocompromised patients. However, adenosine is not effective against herpes simplex virus lung infections.