Complications of Varicella Zoster Virus Infection in Children

The complications of VZV infection occur with varicella, or with reactivation of infection, more commonly in immunocompromised patients. In the otherwise healthy child, mild varicella hepatitis is relatively common but rarely clinically symptomatic.

Mild thrombocytopenia occurs in 1–2% of children with varicella and may be associated with transient petechiae. Purpura, hemorrhagic vesicles, hematuria, and gastrointestinal bleeding are rare complications that may have serious consequences.

Cerebellar ataxia occurs in 1 in every 4,000 cases. Other complications of varicella, some of them rare, include encephalitis, pneumonia, nephritis, nephrotic syndrome, hemolytic-uremic syndrome, arthritis, myocarditis, pericarditis, pancreatitis, and orchitis.

Secondary Bacterial Infections.
Secondary bacterial infections of the skin, usually caused by group A streptococci and S. aureus, may occur in up to 5% of children with varicella. These range from superficial impetigo to cellulitis, lymphadenitis, and subcutaneous abscesses. An early manifestation of secondary bacterial infection is erythema of the base of a new vesicle. Recrudescence of fever 3–4 days after the initial exanthem may also herald a secondary bacterial infection. Varicella is a well-described risk factor for serious invasive infections caused by group A streptococcus, which can have a fatal outcome. The more invasive infections, such as varicella gangrenosa, bacterial sepsis, pneumonia, arthritis, osteomyelitis, cellulitis, and necrotizing fasciitis, account for much of the morbidity and mortality of varicella in otherwise healthy children. Bacterial toxin-mediated diseases (toxic shock syndrome) also may complicate varicella. A substantial decline in varicella-related invasive bacterial infections has been associated with the use of the varicella vaccine.

Encephalitis and Cerebellar Ataxia.
Encephalitis (1/50,000 cases of varicella) and acute cerebellar ataxia (¼,000 cases of varicella) are well-described neurologic complications of varicella; morbidity from CNS complications is highest among patients younger than 5 yr or older than 20 yr. Nuchal rigidity, altered consciousness, and seizures characterize meningoencephalitis. Patients with cerebellar ataxia have a gradual onset of gait disturbance, nystagmus, and slurred speech. Neurologic symptoms usually begin 2–6 days after the onset of the rash but may occur during the incubation period or after resolution of the rash. Clinical recovery is typically rapid, occurring within 24–72 hr, and is usually complete. Although severe hemorrhagic encephalitis, analogous to that caused by herpes simplex virus, is very rare in children with varicella, the consequences are similar to herpes encephalitis.

Reye syndrome of encephalopathy and hepatic dysfunction associated with varicella has become rare since salicylates are no longer routinely used as antipyretics .

Pneumonia.
Varicella pneumonia is a severe complication that accounts for most of the increased morbidity and mortality in adults and other high-risk populations, but pneumonia may also complicate varicella in young children. Respiratory symptoms, which may include cough, dyspnea, cyanosis, pleuritic chest pain, and hemoptysis, usually begin within 1–6 days after the onset of the rash. Smoking has been described as a risk factor for severe pneumonia complicating varicella. The frequency of varicella pneumonia may be greater in the parturient and may lead to premature termination of pregnancy.