This summary discusses varicella in children. Neonatal varicella is addressed separately.
Varicella, or chickenpox, is an acute, highly contagious exanthem caused by primary infection with varicella-zoster virus (VZV). The virus is believed to be spread by respiratory droplets and skin vesicles from individuals with varicella or herpes zoster (a dermatomal rash caused by reactivated endogenous VZV) to the respiratory tract of susceptible children. In immunologically normal children, the illness typically begins after an incubation period of 2-3 weeks, lasts 3-7 days, and resolves without complication. One varicella episode usually confers lifelong immunity, although reinfections have been documented.
In rare cases, varicella is associated with prolonged courses and severe complications, including bacterial superinfection, pneumonia, encephalitis, bleeding disorders, and hepatitis. Adolescents and immunocompromised children (eg, malignancy, congenital defects in cell-mediated immunity, organ transplant recipients, children receiving long-term immunosuppressive therapy, or human immunodeficiency virus [HIV]-infected children) are at elevated risk for complications.
Varicella was a common viral disease of children until childhood vaccination in the United States became routine during the 1990s. The disease remains common in nondeveloped countries and is seen more frequently in older children and adults.
In vaccinated individuals, "breakthrough varicella" can occur. Illness is usually mild (low fever or no fever, fewer lesions [less than 50], less pruritic, shorter duration, absence of vesicles), although some patients present similar to unvaccinated individuals.
Miliaria crystallina – No viral symptoms; lesions do not rapidly progress to pustules and crusts.
Disseminated herpes simplex virus (HSV) – Concentrated in sites typically infected by HSV (oral mucosa, perioral area, and genitalia) and occurs in patients with depressed immunity or underlying dermatoses.
Impetigo – Gradually progressive, superficial erosions, very fragile bullae, and favors exposed sites.
Insect bite reactions – Larger papules and vesicles, and lesions do not rapidly progress to pustules and crusts; favor exposed sites.
Molluscum contagiosum – No viral symptoms; lesions do not rapidly progress to pustules and crusts.
Pityriasis lichenoides et varioliformis acuta (PLEVA) – Recurrent crops of papulovesicles that crust and resolve with residual hypopigmentation, less pruritus, and no mucous membrane involvement.
Gianotti-Crosti syndrome – Lesions are monomorphic edematous papules (in contrast to various stages of lesions seen with PLEVA).
Variola (smallpox) – All lesions at the same stage; favors extremities. Note: this disease has been eradicated; therefore, it would only be diagnosed in the event of a bioterrorist act.
