The vesicular rash in a dermatomal distribution is most likely due to which virus?

• A. Varicella-zoster virus
• B. Herpes simplex virus
• C. Epstein-Barr virus
• D. Cytomegalovirus

Answer: (A)

A vesicular rash that appears in a single, unilateral band along a dermatome is classic for reactivation of varicella-zoster virus, causing herpes zoster (shingles). After initial varicella infection, the virus becomes latent in dorsal root ganglia and can reactivate later, traveling along sensory nerves to the skin in that specific dermatomal pattern. The eruption typically shows vesicles on an erythematous base and is often painful.

Herpes simplex usually causes grouped vesicles at mucocutaneous sites (like the lips or genitals) and does not characteristically follow a dermatomal distribution. Epstein-Barr virus and cytomegalovirus infections do not present with a dermatomal vesicular rash; they cause systemic symptoms such as mononucleosis-like illnesses or organ-specific complications in certain settings.