Rosh Pediatrics Practice Exam

In a 12-month-old with a fever followed by a rash, what is the most likely diagnosis?

1. Erythema infectiosum

2. Roseola infantum

3. Rubella

4. Scarlet fever

The correct answer is: Roseola infantum

In a 12-month-old child, the presentation of a fever followed by a rash is highly indicative of roseola infantum, also known as sixth disease. This viral infection is most commonly caused by the human herpesvirus 6 (HHV-6) and typically affects infants and young children, often between 6 months and 2 years of age. The classic progression starts with a high fever that can last for three to five days. Once the fever resolves, a characteristic rose-colored rash appears, usually starting on the trunk and then spreading to the face and extremities. This pattern of fever followed by the onset of a rash is a hallmark of roseola, making it the most likely diagnosis in this scenario. Other conditions may present with similar symptoms but typically do not follow this specific pattern. Conditions like erythema infectiosum (fifth disease) are often associated with parvovirus B19 and generally present with a "slapped cheek" appearance and can be preceded by mild flu-like symptoms. Rubella typically presents with a rash that appears concurrently with mild fever and lymphadenopathy, not a significant fever preceding it. Scarlet fever is characterized by a sandpaper-like rash accompanied by a high fever and often a sore throat,