A 77-year-old woman presented with a one-week history of painful skin lesions over the sacral area. She enjoyed good past health and was not on regular medications. She recalled a similar episode of painful eruptions at the same site ten years ago.
Physical examination revealed crops of vesiculo-pustular leions on an erythematous base at the sacral area. Some lesions have ruptured to form shallow erosions. Other body parts and mucosal surfaces were unaffected. Complete blood count and blood biochemistry were unremarkable.
Herpes simplex reactivation
Differential diagnoses in this case include herpes zoster and superficial fungal infections. Viral swab taken at the base of the erosions showed positive culture for type 1 herpes simplex virus. The patient was treated with a five-day course of oral acyclovir (200mg five times per day). There was complete resolution of the lesions at the end of the anti-viral therapy.
Herpes simplex virus (HSV) is a double-stranded DNA virus. Infection can be caused by either HSV-1 or HSV-2 at the mucosal surface or at sites of skin abrasions. Patients typically present with painful, grouped, small vesicles or pustules on an erythematous base. Herpetic lesions are characterized by the recurring nature as reactivation of the virus at the primary site of infection is common. Lesions can occur anywhere, however HSV-1 is mostly associated with lesions in the oral-labial area (herpes labialis) and HSV-2 with genital lesions (herpes genitalis). Herpes labialis (cold sores) is the most common presentation of oral HSV infection.
The incubation period from the time of exposure to appearance of skin lesions is around 4 to 10 days. Patients may present with fever which usually lasts for 3 to 5 days in patients with a primary infection. Most lesions will resolve in 2 weeks’ time. Upon recurrence, constitutional symptoms are uncommon and if present, are usually much less severe than during primary infection. Lesions tend to crust within 4 to 5 days and heal completely in 10 days. Primary herpes infection and reactivation is not uncommon at the lumbosacral and perineal region (as in the present case), where skin abrasions are common. Risk factors for viral reactivation include old age, immunodeficiency and stress. An important complication of herpes infection is erythema multiforme, which usually follow recurrent herpetic eruptions by 7 to 10 days.
Acyclovir is a selective inhibitor of HSV DNA synthesis which acts on virus-specific thymidine kinase. A dosage of 200mg five times per day for 7 to 10 days is the treatment of choice for primary herpes infection to decrease pain, retard formation of new lesions, shorten duration of viral shedding and time for healing. However, it has no value in preventing recurrences. Most cases of recurrent herpes are mild and do not require therapy. Moreover, the dose of acyclovir should be adjusted in cases of renal impairment. Other anti-viral agents of the same class include valacyclovir and famciclovir. Herpetic lesions are prone to secondary bacterial infection. Wound dressing, local or systemic antibiotics should be commenced when indicated. Adequate pain control is also important in symptomatic patients.