Herpes Zoster in the C3 Dermatome
For 3 days, a 44-year-old man had several crops of tiny vesicles with raised erythematous bases on the right side of his neck and 2 elongated maculopapular lesions at the base of the neck. All of the lesions were within the C3 dermatome.
The patient complained of an intermittent pain that seemed to shoot into his right ear; however, the rash was not painful or pruritic. Vesicular fluid was found positive for varicellazoster virus by immunofluorescent monoclonal antibody staining in spinamplified shell vial culture.
Herpes zoster usually affects a single dermatome. Infrequently, adjacent dermatomes are involved. The virus enters the cutaneous nerves—typically during a previous case of varicella earlier in life or transplacentally—and resides in a dorsal root ganglia. Activation of the virus can result from any of a host of factors that decrease the immune response, such as age, stress, radiation exposure, fatigue, and cancer chemotherapy. The virus migrates down a sensory nerve to the skin where clusters of vesicles erupt within the dermatome. Successive crops of lesions can develop for about 7 days.
Pain may precede the eruption by several days; pain experienced several weeks in advance is much less frequent. The pain may mimic pleurisy, myocardial infarction, migraine, or acute abdominal conditions.
Current antiviral treatments include acyclovir, famciclovir, and valacyclovir given orally for 7 days. They are most effective in reducing acute and post-herpetic neuralgia when begun within 72 hours of the onset of the rash. The use of oral corticosteroids is controversial.
This patient was treated with oral famciclovir, 500 mg tid. The rash and pain resolved completely in about 3 weeks.