March 2006

This 11-month-old boy presented with a four-day history of vesicular rash with erosions and desquamation. The rash initially appeared on his trunk, then progressed to the rest of his body. His review of systems was positive for fever (101.8ºF) and irritability, as well as cough and rhinorrhea one week prior to presentation. He received either acetaminophen (Tylenol, Ortho-McNeil) or ibuprofen for his fever, according to his mother’s history. He has a sister who was seen about two weeks prior for a skin eruption on her arm, which was diagnosed as pityriasis rosea. What do you think is the diagnosis?

Answer

This patient had varicella with superimposed Staphylococcus aureus. An initial Tzanck test was negative. His cultures were positive for methicillin-sensitive S. aureus. He was initially treated with IV acyclovir, clindamycin, oxacillin and vancomycin. Oral acyclovir, linezolid (Zyvox, Pfizer) and cephalexin were administered when the diagnoses of varicella and S. aureus were made.

Varicella zoster virus is a herpes virus responsible for varicella (chickenpox) and herpes zoster (shingles). Varicella occurs in 90% of U.S. children before age 10 years. The incubation period may last 14 to 16 days, with a one- to three-day prodrome consisting of fever, respiratory symptoms and headache, especially in older patients. The exanthem consists of pruritic red macules that rapidly develop into vesicles with surrounding erythema, giving the characteristic “dew drop on a rose petal” appearance; these then form pustules that scab over. The lesions are typically found on the trunk and face; however, the scalp and mucosal surfaces may also become involved.

The most common complication is secondary bacterial infection (2% to 3% of children) with staphylococci or group A streptococci. Staphylococcal infections may be toxin-mediated (scalded skin syndrome, toxic shock syndrome) or suppurative (impetigo, abscesses). Other complications from varicella include encephalitis, thrombocytopenia, arthritis, hepatitis, cerebellar ataxia, meningitis and glomerulonephritis. Immunocompromised patients may develop varicella pneumonia or hemorrhagic varicella lesions.

Transmission occurs most commonly through respiratory droplets. Infection through direct contact with vesicular fluid is also possible.

Varicella is usually diagnosed clinically from the history and physical. Tzanck smear from an intact vesicle may demonstrate multinucleated giant cells. The diagnosis may also be made from direct fluorescent antibody staining or viral culture of fluid from a fresh vesicle.

The differential diagnosis includes herpes simplex virus, vesicular viral exanthems (coxsackie, enterocytopathic human orphan), impetigo, papular urticaria, scabies, drug eruption, contact dermatitis or folliculitis.

Treatment consists of supportive measures such as antipyretics, antihistamines, calamine lotion and tepid baths. Salicylates should be avoided due to the risk of Reye’s syndrome. Acyclovir given within 24 to 72 hours after onset of rash can result in a modest decrease in duration and symptoms. IV acyclovir is indicated for immunocompromised patients or high-risk neonates. Oral acyclovir should be reserved for immunocompetent patients at increased risk of moderate-to-severe varicella. Famciclovir (Famvir, Novartis) and valacyclovir (Valtrex, GlaxoSmithKline) are other antiviral agents licensed for treatment of adults; safety and efficacy, however, have not been established in children.

The varicella vaccine is more than 95% effective in preventing moderate-to-severe disease, and 70% to 85% effective in preventing mild disease. Recommendations for vaccination are one dose in children 12 years of age or younger, or two doses four to eight weeks apart in patients older than 12. About 1% to 4% of vaccinated children may develop a mild varicellalike reaction consisting of insect bitelike papules, low-grade fever and rapid recovery.

For more information:

• Bolognia, JL, Jorizzo J, Rupini R. Dermatology. Vol.1. Philadelphia, PA: Mosby; 2003: 1241-1243.
• Pickering LK, ed. Staphylococcal infections. In: American Academy of Pediatrics. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003: 573-574, 672-683.
• Pickering LK, ed. Varicella-zoster infections. In: American Academy of Pediatrics. Red Book: 2003 Report of the Committee on Infectious Diseases. 26th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2003: 672-683.