A blackhead is an open comedo, caused by accumulation of keratin and sebum within the opening of a hair follicle.

A blackhead is an open comedo, caused by accumulation of keratin and sebum within the opening of a hair follicle.

• A. Verruca
• B. Steatoma
• C. Blackhead
• D. Milia

Answer: (C)

The concept being tested is recognizing an open comedo, or blackhead. A blackhead forms when keratin and sebum accumulate in the opening of a hair follicle, keeping the pore open. When exposed to air, the material oxidizes and turns dark, giving the characteristic black appearance. This differentiates it from a whitehead, which is a closed comedo with a pale interior. The other conditions are not open comedones: a verruca is a wart caused by HPV with a rough surface; a steatoma is a sebaceous cyst that forms a lump beneath the skin; milia are tiny white keratin-filled cysts under the skin.

The concept being tested is recognizing an open comedo, or blackhead. A blackhead forms when keratin and sebum accumulate in the opening of a hair follicle, keeping the pore open. When exposed to air, the material oxidizes and turns dark, giving the characteristic black appearance. This differentiates it from a whitehead, which is a closed comedo with a pale interior. The other conditions are not open comedones: a verruca is a wart caused by HPV with a rough surface; a steatoma is a sebaceous cyst that forms a lump beneath the skin; milia are tiny white keratin-filled cysts under the skin.