A young child presents with the facial rash shown in the image. Which of the following is the most likely diagnosis?

Explanation

## Image Findings * Bilateral, intensely erythematous rash affecting both cheeks. * The rash gives a characteristic "slapped-cheek" appearance. * Relative sparing of the perioral area and forehead. * The child appears to be an infant or young toddler. ## Diagnosis **Key Point:** The characteristic "slapped-cheek" appearance on the face of a child is pathognomonic for **Erythema Infectiosum (Fifth Disease)**. Erythema Infectiosum is caused by **Parvovirus B19**. It typically presents in three stages: 1. **Prodromal phase:** Mild fever, headache, coryza (often missed). 2. **Erythematous facial rash:** The classic "slapped-cheek" appearance, as seen in the image, due to intense erythema on the malar eminences, often with circumoral pallor. 3. **Reticular (lacy) rash:** A few days later, a lacy, erythematous, pruritic rash appears on the trunk and extremities, which can wax and wane for weeks. ## Differential Diagnosis | Feature | Erythema Infectiosum (Fifth Disease) | Scarlet Fever | Measles (Rubeola) | Roseola Infantum (Sixth Disease) | | :------------------ | :----------------------------------------------------------------- | :----------------------------------------------------------------------------- | :----------------------------------------------------------------------------- | :----------------------------------------------------------------------------- | | **Causative Agent** | Parvovirus B19 | *Streptococcus pyogenes* (Group A Strep) | Measles virus | HHV-6, HHV-7 | | **Rash Appearance** | "Slapped-cheek" facial rash, followed by lacy rash on trunk/limbs. | Diffuse erythematous, "sandpaper" rash, circumoral pallor, strawberry tongue. | Maculopapular, confluent rash starting on face/behind ears, spreading downwards. | High fever for 3-5 days, then rash appears as fever breaks (trunk to extremities). | | **Prodrome** | Mild, often asymptomatic. | Sore throat, fever, headache. | Cough, Coryza, Conjunctivitis (3 Cs), Koplik spots. | High fever, often without other symptoms. | | **Image Findings** | Matches the "slapped-cheek" appearance. | Does not show diffuse sandpaper rash or typical circumoral pallor. | Does not show generalized maculopapular rash or Koplik spots. | Rash appears *after* fever breaks, typically on trunk. | ## Clinical Relevance **Clinical Pearl:** Erythema Infectiosum is generally a benign childhood illness. However, it can cause **aplastic crisis** in individuals with chronic hemolytic anemias (e.g., sickle cell disease, thalassemia) due to its tropism for erythroid progenitor cells. It can also cause **hydrops fetalis** if a pregnant woman contracts it, especially in the first trimester. ## High-Yield for NEET PG **High-Yield:** The classic "slapped-cheek" rash is the most recognizable feature of Erythema Infectiosum. **Key Point:** Parvovirus B19 is the causative agent. Transmission is primarily respiratory. ## Common Traps **Warning:** Do not confuse the facial flushing of scarlet fever with the distinct "slapped-cheek" appearance of Fifth disease. Scarlet fever typically has a more diffuse, sandpaper-like rash and prominent circumoral pallor, but the cheeks themselves are not usually as intensely and sharply demarcated as in Fifth disease. ## Reference [cite:Nelson Textbook of Pediatrics, 21st Edition, Chapter 262: Parvovirus B19]