Roseola infantum

Epidemiology

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• Peak incidence: 6 months to 2 years

Etiology

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• Pathogen
  • HHV-6 (and in rare cases HHV-7)
  • Humans are the sole hosts.
• Route of transmission: droplet infection (e.g., saliva)

Pathophysiology

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Clinical features

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Tip

热退疹出，颜色粉红

Febrile phase

• Duration: 3–5 days
• Fever
  • Abrupt onset of high fever, in some cases > 40ºC (104ºF)
  • Febrile seizures are a potential complication of roseola (see “Complications” below).
• Cervical, postauricular, and/or occipital lymphadenopathy
• Inflamed tympanic membranes
• Nagayama spots: papular enanthem on the uvula and soft palate

Exanthem phase

• Duration: 1–3 days
• Characteristic presentation: subsequent sudden decrease in temperature and development of a patchy, maculopapular exanthem
  • Rose-pink in color; blanches upon pressure
  • Nonpruritic (in contrast to the drug allergy rash)
  • Originates on the trunk; sometimes spreads to the face and extremities

Diagnostics

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Childhood exanthems

Disease	Pathogen	Classic Presentation & Buzzwords
Measles	Measles virus	4 C’s (Cough, Coryza, Conjunctivitis, Koplik spots). Rash: Face $\to$ Body (Confluent). Assoc: Vitamin A deficiency.
Rubella	Rubella virus	Post-auricular LAD. Rash: Face $\to$ Body (spares 3 days, non-confluent). Assoc: Congenital (PDA, cataracts, deaf), Adult arthritis.
Roseola	HHV-6	High fever breaks $\to$ Rash appears. Rash: Trunk $\to$ Face. Assoc: Febrile seizures.
Fifth Disease	Parvovirus B19	”Slapped Cheek” $\to$ Lacy/Reticular body rash. Assoc: Aplastic crisis (Sickle Cell), Hydrops fetalis.
Varicella	VZV	”Dewdrop on a rose petal”. Lesions in different stages of healing. t Rash: Trunk $\to$ Extremities.
Scarlet Fever	Strep pyogenes	Sandpaper rash, Strawberry tongue, Circumoral pallor. Assoc: Strep throat, Desquamation (palms/soles).

Fever-rash relationship

• Measles (Rubeola): Fever first (with cough, coryza, conjunctivitis) → Rash appears 3-5 days later, spreading from head to toe.
• Rubella (German Measles): Low-grade fever → Rash appears 1-2 days later, spreading quickly from head to toe.
• Scarlet Fever: Fever and sore throat begin together → “Sandpaper” rash appears 1-2 days later.
• Erythema Infectiosum (Fifth): Low-grade fever/prodrome resolves → “Slapped cheek” rash appears days later.
• Roseola Infantum (Sixth): High fever for 3-5 days → Fever breaks → Rash appears after the fever is gone.
• Varicella (Chickenpox): Fever and vesicular rash appear at the same time (lesions in various stages).

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Treatment

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