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Chickenpox - Making a diagnosis
How do I know my patient has it?

  • In most cases, the diagnosis can be made clinically from the characteristic chickenpox rash. If there is doubt, a history of recent exposure to varicella (or herpes zoster), or cases occurring in close contacts [Heininger and Seward, 2006], may help confirm the diagnosis.
  • Features of chickenpox include [Heininger and Seward, 2006; Papadopoulos, 2007]:
  • History:
    • Chickenpox (especially in adults and adolescents) may start with a prodrome that includes nausea, myalgia, anorexia, and headache.
    • People with chickenpox may also experience general malaise, loss of appetite, and feeding problems.
  • Examination:
    • Fever.
    • Rash:
      • Small, erythematous macules appear on the scalp, face, trunk, and proximal limbs, which progress over 12–14 hours to papules, clear vesicles (which are intensely itchy), and pustules.
      • Vesicles can also occur on the palms and soles, and mucous membranes can also be affected, with painful and shallow oral or genital ulcers.
      • Vesicles appear in crops; stages of development of the rash can therefore differ on different areas of the body.
      • Crusting occurs within 1–4 days, and crusts fall off after 1–2 weeks.
    • Adults may experience a more widespread rash and more prolonged fever than do children.
  • Investigations:
    • Laboratory tests can be used for confirmation but are rarely required [Lichenstein, 2006]. If confirmation is needed in pregnant women, varicella can be detected by virus, antigen, or genome detection in vesicle fluid and urgent serologic testing for varicella-zoster virus immunoglobulin M [HPA, 2007a].

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