## Parvovirus B19 Rash Characteristics **Key Point:** Parvovirus B19 (erythema infectiosum or fifth disease) presents with a pathognomonic "slapped cheek" appearance — bright red erythema on the cheeks with circumoral pallor. ### Progression of Rash 1. **Phase 1 (Days 1–3):** Intense erythema of cheeks ("slapped cheek" sign) 2. **Phase 2 (Days 4–7):** Lacy, reticular, erythematous rash on trunk and extremities 3. **Phase 3:** Rash may recur with fever, exercise, or sun exposure ### Clinical Features | Feature | Details | | --- | --- | | **Age of presentation** | Peak 4–10 years | | **Prodrome** | Mild fever, malaise, arthralgia (more common in adults) | | **Rash onset** | After prodrome resolves ("slapped cheek" first) | | **Pruritus** | Common, may be intense | | **Contagiosity** | Highest during prodromal phase; non-infectious by rash stage | **Clinical Pearl:** The rash is NOT present during the viremic phase; by the time the characteristic rash appears, the patient is no longer contagious. **High-Yield:** Parvovirus B19 is the only exanthem with the "slapped cheek" sign — this makes it the single most recognizable viral exanthem in pediatrics. [cite:Nelson Textbook of Pediatrics 21e Ch 267]
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