A small child presents with a low-grade fever, coryza, sore throat, a bright red rash on his cheeks, and a less intense erythematous rash on his body. Elevated IgG and IgM antibody titers to parvovirus suggest a diagnosis of which of the following?

**Core Concept**
The child's presentation is suggestive of a viral infection, specifically erythema infectiosum, also known as fifth disease. This condition is caused by the parvovirus B19, which leads to a characteristic "slapped cheek" appearance due to the bright red rash on the cheeks.

**Why the Correct Answer is Right**
The correct diagnosis of erythema infectiosum is supported by the presence of elevated IgG and IgM antibody titers to parvovirus B19. The IgM antibodies indicate recent infection, while the IgG antibodies suggest past exposure and immunity. The rash is a result of the parvovirus B19 infecting the erythroid progenitor cells in the bone marrow, leading to a decrease in erythropoiesis and the characteristic rash.

**Why Each Wrong Option is Incorrect**
**Option A:** Erythema multiforme is a different skin condition characterized by target lesions, which is not consistent with the child's presentation.
**Option B:** Scarlet fever is caused by Streptococcus pyogenes and presents with a sandpapery rash and a distinctive strawberry tongue, which is not seen in this child.
**Option C:** Roseola infantum is a viral infection that presents with high fever and a rash that appears after the fever resolves, which is not consistent with this child's symptoms.

**Clinical Pearl / High-Yield Fact**
Erythema infectiosum is often referred to as "fifth disease" because it was the fifth disease described by dermatologist William Osler in 1889.

**Correct Answer:** C.

✓ Correct Answer: B. Fifth disease