Examining Exanthems!

What is an exanthem anyway?

• “A widely spread out rash” – Google
• “Eruptive disease (such as measles) or its symptomatic eruption” – Merriam-Webster Dictionary
• History and Etymology: Late Latin exanthema, from Greek exanthēma, from exanthein to bloom, break out, from ex- + anthos flower

Most common exanthems are viral, drug-related, or bacterial, and may be associated with systemic symptoms.

Exanthems tend to be macular, maculopapular, papular, or vesicular / pustular. They differ from enanthems, which occur inside the body (e.g. mucous membranes.)

Measles (aka rubeola)

• 3 C’s: cough, coryza, conjunctivitis
• Fever, malaise
• Enanthem: Koplik spots
• Exanthem: maculopapular rash, typically begins 2-4 days after onset of fever
• Rash classically begins on face and spreads to neck, trunk, extremities
• Complication: Subacute sclerosing panencephalitis (SSPE), which is caused by persistent infection of the CNS with the virus

Rubella

• Prodrome: fever, headache, sore throat, myalgias
• Exanthem: maculopapular rash starts on face, then spreads to trunk and extremities, becomes generalized in 24 hrs
• Similar rash to measles, but spread is much more rapid and rash does not darken or coalesce
• LAD (posterior cervical, posterior auricular, suboccipital)
• Arthralgias (teenagers, adult women)

Varicella 

• Prodrome: fever, malaise, pharyngitis, loss of appetite
• Exanthem: pruritic vesicular rash, begins as macules that rapidly become papules followed by characteristic vesicles
• Rash appears in successive crops over several days, most lesions crust over within 6 days
• ~20% children who receive one dose of varicella vaccine may develop varicella infection “breakthrough disease” if exposed (often mild disease, maculopapular)

Erythema infectiosum (aka 5th disease)

• Cause: Parvovirus B19
• Prodrome: fever, coryza, headache, nausea, diarrhea
• Exanthem: classic erythematous malar rash with relative circumoral pallor, followed several days later by a reticulated or lacelike rash on trunk/extremities
• Rash thought to be immunologically mediated
• Can cause arthralgias/arthritis (adults), transient aplastic crisis

Roseola (aka 6th disease)

• Cause: HHV-6, may also be caused by HHV-7, enteroviruses, adenovirus, parainfluenza type 1
• 3-5 days of high fever (may exceed 104°C) that resolves abruptly and is followed by development of a rash
  • Rash begins after viremic phase of illness, coincident with development of antibody to HHV-6, suggesting that it may be result from antigen-antibody complexes
• Exanthem: erythematous, blanching, macular/maculopapular rash that starts on neck/trunk and spreads to extremities (rash may also be vesicular)
• Rash typically persists 1-2 days but may come and go within 2-4 hours
• Associations: Palpebral conjunctivitis, edematous eyelids, seizures, LAD (cervical, postauricular, occipital), encephalitis, thrombotic thrombocytopenic purpura
• Complications: seizures, aseptic meningitis, encephalitis, TTP

EBV

• Only 5-10% children with EBV manifest an exanthem
• If amoxicillin or ampicillin is administered, a characteristic bright-red morbilliform eruption almost always occurs
• Most likely results from ampicillin-antibody immune complexes as a consequence of polyclonal B-cell activation
• NOT a “true” drug allergy

Atypical exanthems

• Unilateral laterothoracic exanthem
• Eruptive pseudoangiomatosis
• Coxsackie A16 – Hand, foot, mouth syndrome
• Papular-purpuric gloves and socks syndrome
• Gianotti-Crosti syndrome

Take-home points!

• Exanthems = widespread rash
• Exanthems can be a whole lot of things – viral, drug-induced, bacterial
• Typical exanthems include measles, rubella, varicella, erythema infectiosum, roseola, EBV
• Atypical exanthems are in different patterns and include unilateral laterothoracic exanthem, Coxsackie HFM, Papular-purpuric gloves and socks syndrome, and Gianotti-Crosti syndrome
• History is key to diagnosing exanthems!

Blog post based on Med-Peds Forum talk by Ann Ding, PGY3