The bottoms of your feet have been hurting when you walk and occasionally may itch. On the bottoms of your feet, you notice that there are small sesame-seed shaped lesions that look like calluses or plantar warts. You try the over-the-counter wart-off medications and you have no success in getting rid of what is on your feet. You use a “ped-egg” or pumice stone thinking that maybe they are small calluses, but you still have no relief and the lesions are still visible. What are these small sesame-seed shaped lesions on the bottoms of your feet?
The answer is porokeratosis (plugges sweat gland). Not every case of porokeratosis will present with pain or itching, but the appearance of the lesion being a small sesame-seed shape is usually consistent. Porokeratosis is often times misdiagnosed as a plantar wart or callus, which is problematic since the treatments for all three of these types lesions are different. However, since podiatrists commonly see all three of these lesions, it is easier to determine that the lesion may be porokeratosis versus the even more common plantar wart or callus.
The exact reason why people get porokeratosis cannot be pinpointed to one main cause as there are many forms of porokeratosis, but the most common forms are:
- Disseminated Superficial Actinic Porokeratosis:This is the most common variant of porokeratosis. Disseminated means that the lesions can be found all over the body. It usually consists of numerous very small lesions, which are present on areas of sun-exposed skin. Women are most commonly affected.
- Porokeratosis of Mibelli:This form is commonly found in infants and children. The small lesions are most often times found on the arms and legs, but can develop anywhere. This type of lesion begins as a small rough area, but then expands outward increasing in size over time.
- Punctate Porokeratosis:This variant is more commonly seen in the late teens and adults. This is the variant that can be most painful when it is on the bottom of the foot. There may be several or only one lesion noted.
It used to be thought that porokeratosis were really just plugged sweat glands on the bottom of the foot, but this has been determined as incorrect. However, there is one variant called Eccrine Osteal Porokeratosis, which fits this description. This variant is extremely rare and only makes up 1% of all cases of porokeratosis.
All variants of porokeratosis can be distinguished from plantar warts and calluses with 100% accuracy by taking a small skin biopsy and examining it under the microscope. With the microscope, the presence of cornoid lamella will be noticed. Cornoid lamella is due to an abnormal formation of the skin cells. However, some variants of porokeratosis can be diagnosed without using a microscope based on the appearance and patient symptoms.
To treat porokeratosis, the cornoid lamella needs to be destroyed. There are no over-the-counter treatments for porokeratosis, so only a podiatrist can provide treatment. Some treatment options include:
- Topical prescription medications
- Excising the porokeratosis
- Laser therapy
- Curettage with electrodessication
All of these treatment modalities work to destroy the cornoid lamellae. The Platte Valley Foot and Ankle Clinic will be able to differentiate between calluses, plantar warts, and porokeratosis and will determine, which treatment is best for you. Lastly, it is very important to treat porokeratosis even if you have no symptoms, since these lesions may be a precursor to squamous cell carcinoma. However, this is extremely rare, but it is always best to take precaution.