When A Runner Presents With Painful Plantar Lesions

Brent D. Haverstock, DPM, FACFAS

A 44-year-old competitive runner presented with a history of painful lesions on the plantar aspect of both feet. He stated that the problem initially began with the presence of a single lesion. He denied any history of trauma to the area and indicated that there has never been any bleeding from the site. Further lesions developed and they started to cause some discomfort while he was running.

   After discussing his problem with one of his running partners, the patient started treating the lesions as plantar warts by applying a topical over-the-counter medication. This did provide some relief as the medication would seem to soften the lesions and the firm callus would fall off. As he continued to run and increase his mileage training for a marathon, he noticed the lesions had become larger.

   He consulted his primary care physician, who agreed with his diagnosis of plantar warts and started treatment with liquid nitrogen. Again, the patient experienced some relief but this was short lived. Further attempts to eradicate the lesions with a stronger topical salicylic acid again failed.

   The patient stated that after several weeks of treatment, which often affected his ability to continue running, he stopped seeing his physician. The lesions would seem to reach a point where they would become problematic and he would apply a corn remover or scrape them away for relief. He says he was always careful to wear flip-flops around the locker room and the shower at the fitness center.

   The patient was fit and related no underlying medical concerns. He stated that he was a non-smoker and occasionally drank red wine. He denied any use of illegal drugs or a history of sexually transmitted disease.

   The neurovascular examination was normal. The orthopedic examination was also non-contributory. Upon close inspection of the plantar aspect of both feet, I noted multiple well demarcated, hyperkeratotic nodules on the weightbearing areas beneath the second and fourth metatarsal heads of the right foot, and the third metatarsal head on the left foot. The lesions varied in size from 1 mm to 3 mm in diameter.

   The lesions also demonstrated a white or white-yellow discoloration. There was pain with side-to-side compression of the lesions. Examination of the lesions under magnification revealed the presence of skin striations within the lesions.

   Further examination did not reveal any lesions on the skin around the scalp, the palmar surface of the hands, or the flexor and extensor surfaces of the elbows and knees. The oral cavity was likewise devoid of any form of plaques or lesions.

Key Questions To Consider

1. What are the characteristics of the lesions of this disease?
2. What is the most likely diagnosis?
3. What is your differential diagnosis?
4. What does the histologic examination reveal?
5. What is the best course of treatment?

Answering The Key Diagnostic Questions

1. The lesions are characterized by an area of hyperkeratotic tissue with a central nucleated core with a white or yellow-white appearance. There is tenderness with side-to-side compression of the lesion.
2. Porokeratosis plantaris discreta
3. Differential diagnoses include plantar verrucae, intractable plantar keratosis, arsenical keratosis, pyogenic granuloma and eccrine poroma.
4. The histologic exam shows a cornoid lamella and transepidermal elimination of blood vessels and collagen fibers.
5. Treatment includes debridement of the lesion, offloading and salicylic acid 40%. Other options are intralesional injection therapy and cryosurgery.

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