Clinical Challenge: Itchy Blisters with a Sore Throat

Chickenpox—or varicella—is the consequence of the primary infection with the varicella zoster virus (VZV). The varicella zoster virus is a double-stranded DNA virus in the family of herpes viruses. There is currently a vaccine against VZV; therefore, chickenpox has become...

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Chickenpox—or varicella—is the consequence of the primary infection with the varicella zoster virus (VZV). The varicella zoster virus is a double-stranded DNA virus in the family of herpes viruses. There is currently a vaccine against VZV; therefore, chickenpox has become more rare in the U.S.

More than 90% of U.S. adults have immunologic immunity to VZV, which indicates prior infection with VZV. Most adults recall having had chickenpox as children. 

Transmission from direct contact with the blisters is theoretically possible, but the vast majority of cases are respiratory transmissions. Infected individuals are most infectious several days prior to the onset of the rash, and remain infections until approximately six days after the appearance of the rash. The incubation period is usually 14 to 15 days at which point the patient develops the eruption accompanied by mild headache, fever and malaise. 

Adults have significantly more severe disease than children. The death rate is 30 times greater in adults than children. Pregnant women and immunosuppressed individuals experience more severe disease and worse outcomes. After chickenpox patients develop lifelong immunity, but the virus may remain dormant in the dorsal root ganglia of the sensory nerves. 

Herpes zoster represents a reactivation of the VZV.  A second “bout of chickenpox” actually represents disseminated herpes zoster, and not chickenpox. This may occur in immunosuppressed individuals. 

The classic primary varicella lesion is a faint macule that quickly develops into a vesicle on an erythematous base. These have been described as “dewdrops on a rose petal.”  Lesions develop in crops and may occur in the mouth. Older lesions become pustular and then crusted.

The most common complication of varicella is bacterial superinfection of the lesions.  Pneumonia is seen in 1 in 400 adults and has a 10% to 30% mortality rate if untreated.  Other complications include encephalitis and cerebellar ataxia, myocarditis, hepatitis and symptomatic thrombocytopenia. Reye syndrome is a syndrome of hepatitis and encephalopathy and may occur when aspirin is used to treat varicella. Therefore aspirin is absolutely contraindicated when there is suspicion of varicella. 

Varicella diagnosis is based on the characteristic appearance of the rash. The most helpful laboratory test is the direct fluorescent antigen test (DFA). Viral culture is a poor test.

Complications of varicella in healthy children are rare, so deciding whether to treat a healthy child needs to be made on a case-by-case basis. All individuals older than 13 years should be treated due to both the increased disease severity and the increased risk for complications. Treatment consists of oral or IV acyclovir. 

Pregnant women with varicella may suffer severe and complicated disease. Additionally, infections during the first 20 weeks of pregnancy may result in congenital varicella syndrome in which the fetus develops multiple anomalies. All pregnant patients with confirmed or suspected varicella must be treated with acyclovir. 

The varicella zoster immune globulin (VZIG) is reserved for several high-risk groups including seronegative pregnant women, immunosupressed individuals and neonates who have been exposed to varicella. It should be administered within the first 96 hours following exposure. 

Today, chickenpox is rare due to the live-attenuated varicella vaccine, which is administered in two doses — at 12 to 15 months and again at 4 to 6 years. A mild skin eruption may occur within the first two weeks following vaccination. Additionally, immunized children may develop a modified varicella-like syndrome after exposure to natural VZV. This consists of a mild rash, usually without any systemic symptoms.

Adam Rees, MD, is a graduate of the University of California Los Angeles School of Medicine and a resident in the Department of Dermatology at Baylor College of Medicine in Houston.