infectious diseases
Herpes Simplex Virus (HSV) Infections
Diagnosis of Herpes Simplex Virus
History and physical examination Sometimes laboratory confirmation Polymerase chain reaction (PCR) of cerebrospinal fluid (CSF) and MRI for HSV encephalitis Diagnosis of HSV infection is often clinical based on characteristic lesions. Laboratory confirmation can be helpful, especially if infection is severe, the patient is immunocompromised or pregnant, or lesions are atypical. A Tzanck test (a superficial scraping from the base of a freshly ruptured vesicle stained with Wright-Giemsa stain) often reveals multinucleate giant cells in HSV or varicella-zoster virus infection. Definitive diagnosis is with culture, seroconversion involving the appropriate serotype (in primary infections), PCR, and antigen detection. Fluid and material for culture should be obtained from the base of a vesicle or of a freshly ulcerated lesion. HSV can sometimes be identified using direct immunofluorescence assay of scrapings of lesions. PCR of CSF and MRI are used to diagnose HSV encephalitis. HSV should be distinguished from Herpes Zoster , which rarely recurs and usually causes more severe pain and larger groups of lesions that are distributed along a dermatome and typically do not cross the midline. Clusters of vesicles or ulcers on an erythematous base are unusual in genital ulcers other than those due to HSV infection. If herpes infections recur frequently, do not resolve, or do not respond to antivirals as expected, immunocompromise, possibly due to Human Immunodeficiency Virus (HIV) Infection , should be suspected. 