What is the Difference Between a Callus, Corn, Porokeratosis, and a Wart?

A callus is an area of thickened skin most often found on the bottom of the foot, side of a bony prominence, or on the heels. There are a number of reasons why a callus forms. Sometimes a callus may form over a bony prominence caused by a foot deformity, such as with a bunion bump.  When someone has a prominence from a bunion deformity, pressure from walking or even friction from wearing shoes can cause the skin to form extra layers resulting in a callus lesion.  A callus may also form under the forefoot due to mechanical or biomechanical pressures from the way the foot functions. Foot deformities or malalignments can lead to instability of parts of the foot, which in turn can lead to shifts in pressure from one area of the foot to another resulting in a callus lesion. A corn is a type of callus that forms on the toes.   Someone with a hammertoe deformity, which causes a prominence on top of the toe, may develop corns.  Corns can cause someone pain as a result of friction from wearing shoes.


A porokeratosis is a small, round “seed” corn or callus on the bottom of the foot or side of the arch typically caused by a clogged sweat gland of the skin. Someone with porokeratosis usually experiences pain with direct pressure if the lesion is on a weight-bearing area of the foot.

Plantar Wart

A wart is a viral infection of the skin. The virus infects the top layer of the skin called the epidermis and causes a painful, thick skin lesion.  A wart has a “cauliflower” appearance and usually has small, black, pin-point capillaries, which can cause these lesions to bleed easily. Someone with a wart usually experiences more pain with a side-to-side compression compared to direct pressure on the wart.

It is very important to have the correct diagnosis for your skin lesion because they each require different forms of treatment.

For more information, contact us at Olympic Foot and Ankle at 916.244.7630.