chickenpox

Etiology

• primary infection with Varicella zoster virus
• immunosuppression (including systemic steroids) increases susceptibility

Epidemiology

• no gender or race predilection
• seasonal peak late winter, early spring
• generally affects children
• transmitted via airborne respiratory droplets or direct vesicle contact

Pathology

• incubation 10-20 days
• infectivity
  • begins 48 hours prior to onset of symptoms
  • persists through period of new lesion formation (3-5 days)

Clinical manifestations

• prodrome of low-grade fever, malaise & pharyngitis may precede rash by 24-48 hours
• 1st lesions generally appear as erythematous vesicles on trunk &/or face
• lesions appear in crops such that lesions in different phases of development are present at any one time
• lesions spread centripetally to involve entire skin surface & possibly mucous membranes
• rash is vesiculopapular
  • new clear vesicles 3-5 mm in diameter on an erythematous base, described as dewdrop on a rose petal
  • older cloudy vesicles may progress to pustules or crusted papules
  • multiple stages of lesions present at the same time,* i.e. a mix of vesicles, papules, pustules, crusted erosions, scabs
  • new lesions cease appearing in 3-7 days
• lesions are pruritic
• scratching may result in excoriations &/or cellulitis
• constitutional symptoms occur at the same time as rash*
  • low-grade fever (100-103 F)
  • myalgias
  • headaches
• symptoms may be more severe in elderly or immunocompromised patients
• images

* distinguishing features from smallpox

Laboratory

• diagnosis generally clinical, no laboratory tests usually required
• Varicella-zoster virus DNA is test of choice
• serology
  • acute & convalescent varicella serum titers
  • ELISA or DFA
• Tzanck smear
• tissue culture
• skin biopsy
• gram stain or bacterial cultures of superinfected lesions
• see ARUP consult

Complications

• aspirin use during varicella infection in children may result in Reye syndrome
• complications more common in elderly & immunocompromised
  • pneumonia
  • nephritis
  • myocarditis
  • arthritis
  • meningitis
  • encephalitis
  • transverse myelitis
  • optic neuritis
  • cellulitis
  • thrombotic thrombocytopenic purpura (TTP)
  • purpura fulminans

Differential diagnosis

• atypical presentation of measles
• impetigo
• Herpes simplex virus
• enterovirus, especially coxsackie A
• smallpox:
  • fever precedes rash by 2-3 days
  • rash is in the same stage in different locations at any one time, i.e. all vesicles, all papules, all pustules, all scabs

Management

• symptomatic treatment generally sufficient
  • good hygiene
  • anti-pruritics
    • calamine or other topical anti-pruritic agents
    • oral antihistamines
      • diphenhydramine (Benadryl)
        • children: 5 mg/kg/day PO divided every 6 hours
        • adults: 25-50 mg PO TID-QID
      • hydroxyzine (Atarax)
        • children: 2 mg/kg/day PO divided every 6 hours
        • adults: 25-200 mg PO TID-QID
  • control fever with acetaminophen (Tylenol): DO NOT USE ASPIRIN!
• Antiviral therapy for patients with complications & high-risk patients
  • children 2-12 years: acyclovir (Zovirax) 20 mg/kg QID for 5 days (max 800 mg/day)
  • adults & children > 12 years of age: acyclovir 800 mg PO 5 times/day for 7 days
  • immunocompromised: IV acyclovir 10 mg/kg IV every 8 hours for 7-10 days
• Quarantine until all lesions heal to minimize transmission
• patient education
  • reassurance: chickenpox is generally benign & self-limited
  • AVOID USE OF ASPIRIN!
  • inform family & close contacts of probable secondary outbreaks of chickenpox, including incubation period
• prevention
  • consider prophylaxis for immunocompromised & others
    • VZV immune globulin for up to 96 hours after exposure
    • prevents or lessens severity of infection in otherwise healthy, non-pregnant, susceptible adults
  • isolation for hospitalized patients & for hospital workers through the infectious period
  • Varicella immunization (Varivax) recommended for all individuals who have not had chicken pox
    • children 1-12 years of age: 0.5 mL Varivax SQ
    • children 12-15 months with a 2nd dose at 4-6 years
    • adults & children > 12 years of age: two 0.5 mL doses of Varivax SC 4-8 weeks apart
    • vaccinated individuals can still develop chicken pox, but their clinical course is usually milder than in unvaccinated patients
• chickenpox is a reportable disease

More general terms

• Herpes virus infection

Additional terms

• Herpes zoster (shingles)
• varicella virus vaccine (Varivax)
• Varicella [Herpes] zoster virus (VZV); human herpesvirus 3 (HHV3)