varicella-zoster%20virus%20infection%20(pediatric)
VARICELLA-ZOSTER VIRUS INFECTION (PEDIATRIC)
Varicella, also known as chickenpox, is a self-limited, benign disease caused by primary varicella-zoster virus (VZV) infection characterized by fever, malaise, and generalized pruritic vesicular rash.
The average incubation period is 14-16 days. It is transmitted via direct contact with vesicular fluid or inhalation of aerosolized respiratory secretions or via droplet route during face to face contact.
Hallmark sign is pruritic rash that begins in the scalp and face which eventually spreads to the trunks and extremities.

History

Varicella

  • Determine if the patient had a previous exposure to patient w/ chicken pox
  • Identify immunocompromised patients (HIV-seropositive, leukemia & organ transplant patients)
    • Have higher risk of developing varicella-associated morbidity & mortality
  • Systemic corticosteroid use can also increase morbidity

Herpes Zoster

  • Determine if the patient already had varicella
  • Identify immunocompromised patients (HIV-seropositive, leukemia & organ transplant patients)
    • Have higher risk of developing varicella-associated morbidity & mortality
  • Systemic corticosteroid use can also increase morbidity

Laboratory Tests

Varicella

  • Laboratory confirmation of the diagnosis is not necessary for most cases of varicella but may be necessary in the 2nd episode of varicella, atypical clinical presentation or in cases of drug resistance
  • Culture
    • Gold standard for virologic confirmation, but not highly sensitive due to high lability of varicella zoster virus (VZV)
    • Tzanck smear: Convenient to perform but will not differentiate VZV from herpes simplex virus (HSV)
  • Viral DNA
    • Hybridization & polymerase chain reaction (PCR) are sensitive & specific for the detection of VZV in clinical specimens
    • PCR may also be used to distinguish wild-type from vaccine strains of VZV
  • Serology
    • IgM test lacks specificity
    • Complement fixation test requires paired sera & cross-read w/ HSV
  • Direct & indirect immunofluorescence
    • Fluorescence microscopy: Rapid & sensitive in determining presence of VZV proteins in cells scraped from lesions

Herpes Zoster

  • Clinical diagnosis is sufficient in the typical case of herpes zoster, but laboratory diagnostic testing is useful for differentiating herpes zoster from herpes simplex, for suspected organ involvement & for atypical presentations
  • Culture, serology, direct & indirect immunofluorescence studies are the same w/ varicella

Complications

Varicella

  • Immunocompromised patients, neonates & adults (especially pregnant women) are most at risk for complications
  • Most common complications among healthy children is bacterial superinfection caused by Staphylococcus aureus or Streptococcus pyogenes that manifests as impetigo, furuncles, cellulitis, erysipelas or bullous skin lesions
    • Life-threatening disease known as necrotizing fasciitis has been reported as a complication in children
  • Extracutaneous complications are neurologic which includes acute cerebellar ataxia & meningoencephalitis as major manifestations
    • Reye’s syndrome, transverse myelitis, polyradiculitis, Guillain-Barré syndrome may also occur but are rare
  • Varicella pneumonia is the leading cause of varicella-associated morbidity among adults, pregnant & immunocompromised individuals
  • Transient hepatitis occurs in most children & is usually asymptomatic but fulminant liver failure may occur
  • Immune-mediated thrombocytopenia is associated w/ bleeding into skin lesions, petechiae, purpura, epistaxis, hematuria & gastrointestinal hemorrhage (GI) hemorrhage

Herpes Zoster

  • Postherpetic neuralgia (PHN)
    • PHN is pain that persists in the affected area for >1 month after the lesions have healed
    • Common complication of herpes zoster which is debilitating
    • Incidence of PHN is age related & affects approx 50% of patients >60 year
    • Patient may experience constant pain described as burning, aching or throbbing; intermittent pain described as stabbing or shooting; & stimulus evoked pain [eg allodynia (pain after a non-painful stimulus eg wind or piece of clothing)]
  • Ophthalmic zoster
    • One of the frequent complications of herpes zoster that has the potential to produce corneal damage accompanied by visual impairment, ocular palsy, lid ptosis, conjunctivitis, retinal artery occlusion, panophthalmitis, retinal vasculitis, optic neuritis, choroidal detachment, & visual impairment which may lead to loss of vision
  • Ramsay Hunt Syndrome
    • Involvement of the facial or auditory nerves that can progress to tinnitus, vertigo, deafness, otalgia, loss of taste, nerve palsies
  • Other complications are dermatologic superinfections (impetigo, cellulitis, necrotizing fascitis, herpes gangrenosum); neurologic (meningoencephalitis, myelitis, nerve palsies, altered mentation)
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