Which of the following describes a pustule?

A pustule is specifically defined as a small elevation on the skin that is filled with pus. This characteristic sets it apart from other skin lesions and elevations. The presence of pus within the structure signifies an infectious or inflammatory process, commonly seen in conditions like acne, skin infections, or certain dermatitis types.

The other descriptions refer to different skin phenomena or conditions. A small, circumscribed swelling that protrudes above the skin may refer to a nodule or papule, but does not specifically indicate the presence of pus. A partial-thickness burn from hot objects pertains to burn injuries and is entirely separate from the definitions of skin lesions. Lastly, a condition characterized by absence of pigment refers to conditions like vitiligo or albinism and does not relate to pustules at all. Thus, the description of a small elevation filled with pus accurately captures the defining feature of a pustule.