What is a hard pearl of sebum in the skin that does not have an open lesion?

The correct choice refers to milia, which are small, hard, white cysts that commonly appear on the skin, typically around the eyes and on the cheeks. They form when keratin, a protein found in the skin, becomes trapped beneath the surface. Unlike open lesions, milia do not have an opening; they are sealed cysts that can appear similar to whiteheads but do not express sebum. Milia are benign and often resolve on their own, making them distinct from conditions like acne or comedones, which involve inflammation or blocked pores.

In contrast, a comedone refers to a clogged hair follicle in the skin, which can be either open (blackhead) or closed (whitehead), where there is usually some level of visibility or connection to the skin's surface. Acne is a broader term describing a condition characterized by the presence of inflammatory lesions, clogged pores, and various other factors. A furuncle is an inflamed hair follicle that creates a painful, pus-filled lump—essentially a boil—that also represents an open lesion. Hence, the defining characteristics of milia distinctly differentiate it from the other options provided.