Which of the following is NOT considered a macule?

A macule is defined as a flat, distinct, discolored area of skin that is less than 1 centimeter in diameter. It is an important skin lesion classification.

Freckles are small brown spots caused by an increase in melanin and qualify as macules due to their flat appearance. Petechiae are small, round spots that appear on the skin as a result of bleeding, and since they are also flat and discolored, they are categorized as macules. A flat, 0.5-cm brown birthmark falls within the definition of a macule as well since it is a flat lesion that is less than 1 cm in size and discolored.

Acne, on the other hand, is characterized by raised lesions resulting from inflammation, clogged pores, or infection. Acne presents as papules, pustules, or nodules, which do not fit the definition of a macule because they are not flat; they are elevated above the skin's surface. Therefore, among the options listed, acne is not a macule, making it the correct choice for the question.