A 9- to 12-month-old infant with fever followed by an erythematous maculopapular rash is most consistent with which diagnosis?

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Multiple Choice

A 9- to 12-month-old infant with fever followed by an erythematous maculopapular rash is most consistent with which diagnosis?

The pattern being tested is a fever in a young infant that lasts a few days and then abruptly resolves, followed by a diffuse pink maculopapular rash. This sequence is classic for roseola infantum (exanthem subitum), usually caused by human herpesvirus 6. The fever often runs high for 3–5 days and, as it breaks, the rash appears and spreads, but the child generally looks well once the fever subsides. Understanding the alternatives helps reinforce the distinction: measles typically features fever with cough, coryza, and conjunctivitis, and the rash appears during the febrile illness, starting on the face and spreading downward. Hand-foot-and-mouth disease presents with fever plus vesicular lesions on the hands, feet, and within the mouth rather than a generalized maculopapular eruption. Varicella shows vesicular lesions in crops, primarily pruritic, with a different sequence and distribution than roseola.

The pattern being tested is a fever in a young infant that lasts a few days and then abruptly resolves, followed by a diffuse pink maculopapular rash. This sequence is classic for roseola infantum (exanthem subitum), usually caused by human herpesvirus 6. The fever often runs high for 3–5 days and, as it breaks, the rash appears and spreads, but the child generally looks well once the fever subsides.

Understanding the alternatives helps reinforce the distinction: measles typically features fever with cough, coryza, and conjunctivitis, and the rash appears during the febrile illness, starting on the face and spreading downward. Hand-foot-and-mouth disease presents with fever plus vesicular lesions on the hands, feet, and within the mouth rather than a generalized maculopapular eruption. Varicella shows vesicular lesions in crops, primarily pruritic, with a different sequence and distribution than roseola.

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