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paediatric exanthems

see also:


  • “exanthems” are acute onset rashes with the term usually applied to children with fevers and macular or maculopapular rashes
  • the cause may be viral, bacterial, toxigenic or due to a drug sensitivity
  • in the 19th century, childhood exanthems were classified as:
    • measles
    • scarlet fever
    • rubella
    • “fourth disease” - perhaps misdiagnosis of other exanthems
    • fifth disease - erythema infectiosum
    • sixth disease - roseola infantum
  • although many will be “non-specific” viral exanthems and self-limiting, it is important to diagnose the specific ones where possible for various reasons:
    • strict isolation and contact tracing: eg. measles
    • isolation from school, kindergartens: eg. measles, rubella, chickenpox, fifth disease, etc
    • pregnant mother issues: eg. rubella, parvovirus, chickenpox, zoster
    • need for penicillins: eg. scarlet fever
    • need to avoid amoxycillin/ampicillin: eg. EBV
    • need to exclude serious conditions: eg. meningococcal septicaemia, Kawasaki's, toxic shock syndrome, Steven's Johnson syndrome, Staph Scalded Skin syndrome
    • concern of serious bacterial infection causing high fevers and unnecessary LPs: eg. roseola
    • differentiating from true drug reactions

comparison of the classic childhood exanthems

feature measles scarlet fever rubella erythema infectiosum roseola infantum
aetiology Morbillivirus (Paramyxoviridae) GpA Strept Togaviridae parvovirus B19 human herpesvirus (HHV) types 6 and 7 (Betaherpesvirinae)
incubation 10-12D 1-4D 2-3wks 1-2wks 5-15D
contagious 1-2D before prodrome to 4D after onset rash acute infection, reduces over weeks 5-7D before rash, 3-5D after rash until onset rash intermittent shedding in saliva throughout life
prodrome 3-4D fever, conjunctivitis, rhinitis, sore throat, dry cough, Koplik spots 12-48hrs sudden fever associated with sore throat, swollen neck glands, headache, nausea, vomiting, loss of appetite, swollen and red “strawberry” tongue, palatial petechiae, abdominal pain, body aches, and malaise 2-5D low-grade fever, headache, sore throat and myalgias; occipital LNs; Forschheimer’sspots on hard palate 1-4D slapped cheeks 3-5D high fevers +/- febrile convulsions; abrupt defervescence of fever with appearance of rash
rash coalescing m/p rash starting behind ears, resolving in same order it appears maybe followed by desquamation rash usually starts below the ears, neck, chest, armpits and groin before spreading to the rest of the body over 24 hours; skin lesions progress and become more widespread, they start to look like sunburn with goose pimples. The skin may have a rough sandpaper-like feel m/p with cephalocaudal spread pattern reticulate macular or urticarial exanthem mainly proximal limbs rosey pink, nonpruritic macular rash, predominantly on the neck and trunk when fever abates
other features modified form in vaccinated pts Pastia lines in flexures; desquamation after 6 days, may last 6wks 3rd stage exanthem recurs intermittently in response to stimuli, such as local irritation, high temperatures and emotional stress, 10% children arthropathy (60% adults)
complications acute postinfectious encephalitis 1:1000; delayed SSPE 1:100,000 rheumatic fever, GN, septicaemia, etc cong. rubella syndrome hydrops fetalis leukopenia, rarely, thrombocytopenia and hepatitis

other macular or maculopapular exanthems

Kawasaki's syndrome

  • 80% occur in children under 5yrs
  • high swinging fever (beyond 39C) for at least 5 days with 4 or 5 of the 5 cardinal features:
    • measles-like rash
    • redness within the mouth or on the pharynx, strawberry tongue, and red or cracked lips
    • red eyes
    • firm swelling of the hands and feet, sometimes including the fingers and toes, with redness of the palms and soles
    • lymphadenopathy with at least one gland > 1.5cm long
  • require specific Rx with immunoglobulin, low dose aspirin and follow up Ix as risk of coronary artery aneurysms

non-specific exanthems

  • a number of viruses can cause an exanthem associated with an upper respiratory or gastrointestinal infection
  • nonpolio enteroviruses in the summer months, and rhinovirus, adenovirus, parainfluenza virus, respiratory syncytial virus and influenza virus in the winter
  • Mycoplasma pneumoniae - short-lasting red patches appear on trunk and limbs

hand, foot and mouth

  • caused by Coxsackie A16 virus and related viruses
  • in addition to maculopapular rash, particularly on buttocks, it is characterised by also having mouth ulcers and characteristic purplish vesicles on hands and feet


EBV with amoxycillin or ampicillin

  • most people with EBV / glandular fever / infectious mononucleosis who start amoxycillin or ampicillin develop a rash within 5-9 days of starting the antibiotic
  • the rash is a a characteristic bright-red morbilliform eruption
  • starts on the trunk before becoming generalized as confluent macules and papules
  • it is NOT a true drug allergy as these can be prescribed to the patient later in life without HS reaction

Papular Purpuric Glove & Socks Syndrome (PPGSS)

  • usually caused by parvovirus B19
  • young adults mainly
  • symmetric, painful erythema, and edema of the hands and feet that later progresses to a petechial rash
  • oedema and erythema can be observed on the buccal and genital mucosa, and on the inner aspect of the thighs

Unilateral Laterothoracic Exanthem

  • aka asymmetric periflexuralexanthem of childhood (APEC)
  • ?viral aetiology
  • mainly 1-5yr olds
  • 60-70% have prodrome of rhinitis, pharyngitis, bronchitis, conjunctivitis, gastroenteritis
  • 40-65% have fever
  • macular rash starts in one axilla and extends down side of trunk and arm
  • lasts weeks

Gianotti-crosti syndrome


  • a characteristic response of the skin to viral infection in which there is a papular rash which lasts for several weeks.
  • AKA papulovesicular acrodermatitis of childhood, papular acrodermatitis of childhood and acrodermatitis papulosa infantum


clinical features

  • a profuse papular eruption of dull red spots develops over 3-4 days, first on the thighs and buttocks, then on the outer aspects of the arms, and finally on the face.
  • 5-10 mm in diameter and are a deep red colour
  • may become purple, especially on legs
  • may develop into blisters
  • may be itchy
  • rash lasts 2-8 weeks with mild scaling
  • lymphadenopathy may persist for weeks or months

erythema multiforme

  • classical raised, red, target-like lesions especially limbs then trunk
  • maybe associated with oral and genital lesions
  • may be due to various drugs or infections such as:
    • Mycoplasma pneumoniae
exanthems.txt · Last modified: 2013/10/21 19:18 (external edit)