American Board of Internal Medicine (ABIM) Certification Practice Exam

Which of the following is a key characteristic of the measles rash?

1. Starts as vesicular lesions

2. Initially appears on the arms

3. Begins with small, whitish spots on the buccal mucosa

4. Becomes confluent without blanching

The correct answer is: Begins with small, whitish spots on the buccal mucosa

The key characteristic of the measles rash is the presence of small, whitish spots on the buccal mucosa, known as Koplik spots. These spots are typically observed during the prodromal phase of measles, which occurs before the rash appears. They are considered pathognomonic for the disease and are an important clinical clue. The progression of measles is notable; after the appearance of Koplik spots, a maculopapular rash typically begins on the face and then spreads downward to the trunk and extremities. This pattern helps differentiate measles from other viral illnesses that might present with rash but do not exhibit these distinctive oral lesions. Other characteristics related to the measles rash include that it starts from the head and then moves down the body, and while the rash can become confluent, it does not typically involve vesicular lesions at the onset. Understanding these features is crucial for diagnosis and management in clinical practice.