Kaposi Varicelliform Eruption Workup

Updated: Jun 28, 2022
  • Author: David T Robles, MD, PhD, FAAD; Chief Editor: William D James, MD  more...
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Laboratory Studies

Viral cultures of fresh vesicular fluid and the direct observation of infected cells scraped from ulcerative lesions by direct fluorescent antibody (DFA) staining are the most useful and reliable diagnostic tests available for Kaposi varicelliform eruption (KVE). When cultures are taken, swabbing should be vigorous because herpes simplex virus (HSV) is cell associated and a paucity of extracellular virus particles may be present. DFA staining of scrapings from an early vesicular or crusted lesion is as accurate as viral culture in differentiating HSV-1, HSV-2, and varicella-zoster virus. Furthermore, the results from DFA staining can be available in a few hours.

A Tzanck smear of an opened vesicle or erosion can provide rapid diagnosis when it shows the characteristic epithelial multinucleated giant cells and acantholysis.

If the lesions are atypical, equivocal, or old, biopsy or the polymerase chain reaction (PCR) should be considered. A biopsy can establish a diagnosis that may not have been thought of clinically, whereas PCR can detect minute amounts of viral DNA in tissue through amplification.

Large unstained cells (LUCs) through hematology analysis is a method that has recently been used. This method is beneficial in cases that are often difficult to diagnose when differentiating between KVE and varicella and herpes zoster. In such cases, it has been found that varicella is diagnosed using the LUC method at 71.01% sensitivity and 84.44% specificity rates. [38]

Bacterial superinfection is common in KVE patients, and bacterial culture taken from a moist or crusted lesion often isolates Staphylococcus or Streptococcus.