Comedo

What is a comedo?

A comedo (plural comedones) is a plugged follicular orifice.

• Open comedones (blackheads) are grey, orange, brown or black papules. The keratinous contents can be expressed or extracted. 
• Closed comedones (whiteheads) are uninflamed skin-coloured papules. They must be punctured to remove their contents.

Open comedones

Closed comedones

Which conditions are characterised by a comedo?

Skin lesions and conditions in which there are prominent comedones include:

• Acne, especially acne vulgaris and comedonal acne
• Hidradenitis suppurativa
• Solar (senile) comedones and Favre Racouchot syndrome
• Discoid lupus erythematosus
• A seborrhoeic keratosis (best seen on dermatoscopy)
• A compound or dermal papillomatous melanocytic naevus or mole (best seen on dermatoscopy)
• A comedone naevus
• An epidermal cyst (giant comedo)
• A dilated pore of Winer 
• Enlarged pores.

Comedonal acne

Comedones in hidradenitis suppurativa

Solar comedones

Discoid lupus erythematosus

Dermatoscopy of seborrhoeic keratosis. Rectangles highlight comedones.

Papillomatous naevus

Comedone naevus

Giant comedo

Multiheaded comedo cyst