You walk into the room to see a well-dressed 48-year-old businesswoman sitting in the treatment room. She has her right foot cradled in her hands and is massaging the heel. You notice the stylish high heels on the floor beside her.
“You cannot imagine the pain that I feel, doctor,” she says before you even ask a question. “It feels as though I have a little dagger pressing against my heel. How can there be so much pain from such a tiny little corn?”
When you get a closer look at her foot, you see the patient has applied a pad of skived moleskin. It is not a bad home treatment and may have been suggested by a previous podiatric physician.
By this time, a patient seeking treatment for a “porokeratosis” or “IPK” is frustrated and is “doctor shopping.”
Her history and physical exam show that she has had the 2 mm diameter lesion for six months. The patient says it has increased in size since it was debrided by another DPM. She has had a succession of podiatrists call it a seed corn, a porokeratosis, an intractable keratosis, an IPK and a benign tumor. She calls it excruciating and wants it gone. Your patient wants to know if you can help her for longer than three months at a time.
You ask the patient when the lesion first appeared. The patient thinks for a moment before she answers tentatively. “I think it started when I got a stone bruise when I was training for a half marathon about 12 years ago,” she notes. “It has been getting worse ever since in spite of having it cored out every two to three months. I am getting really frustrated.”
Key Questions To Consider
1. What essential question does one still need to ask to help make the diagnosis?
2. What question should you ask about the location of pain?
3. What feature of this condition differentiates it from other conditions in your differential?
4. What is the differential diagnosis?
Answering The Key Diagnostic Questions
1. Is the lesion under a weightbearing surface?
2. Does it feel like there is a sharp point turned upward, like a knife, into the sole of the foot?
3. There is a white ring around the keratinized core.
4. The differential diagnoses for porokeratosis include an intractable porokeratosis (IPK), palmoplantar wart, punctate porokeratosis and callus.
A Closer Look At Porokeratosis
One of the biggest problems is terminology. Not all podiatric physicians speak the same language. This patient has a hard, keratinized lesion that has developed on the non-weightbearing portion of the heel. This is a porokeratosis or what we know as a porokeratosis. If it were in a weightbearing location, podiatrists would call it an intractable porokeratosis (IPK).
The long held thought that a porokeratosis was a plugged sweat gland has been disproved by multiple scientific methods, including electron microscopy and histologic examination under conventional microscopy. Unfortunately, for unknown reasons, the myth that the porokeratosis is a plugged sweat gland is still being taught at at least one of the podiatric medical schools today even though this has been disproved.
When I started researching this subject, I reached out to the dermatopathology experts in podiatry: Brad Bakotic, DPM, DO, Bryan Markinson, DPM, and G. “Dock” Dockery, DPM.
“In 10 years in my lab, I have seen probably thousands of cases of punctate keratoderma, tens of thousands of IPKs and over 100,000 deep palmoplantar warts, but I have seen only fewer than 20 cases of true ‘punctate porokeratoses,’” notes Dr. Bakotic.1
Dr. Markinson takes a slightly different tack on porokeratoses. “I have biopsied them many times in 25 years and I seem to have gotten back whatever diagnosis I submitted,” he says. “That would include the diagnosis of ‘wart’ when no typical clinical findings existed. Therefore, I have come to believe that early warts may be clinically similar to the porokeratotic lesion.”2
Another well respected dermatology thought leader, Dr. Dockery, weighed in with the following provocative statement and I have come to believe this as well.
“I am not absolutely sure that there is a true entity as the ‘porokeratosis plantaris discreta’ but I do believe there are painful keratotic lesions that form on the foot that are relatively resistant to palliative treatments,” notes Dr. Dockery. “For these lesions, I recommend the sublesional injection of 4% diluted alcohol solution. This will stop the nerve pain and resolve the keratotic lesion in most cases.”3
A Comprehensive Guide To Treatment
Debridement still remains the key principle of treatment for both IPK and porokeratosis. What one does beyond that determines whether the patient must return at the two-month point or is able to delay that return until the four- to six-month point.
On the eTalk blog accessible through www.Podiatry.com, when you search “porokeratosis,” you will find that there have been at least 47,115 views of this thread since my friend and former University of Texas Health Science Center faculty member John Steinberg, DPM, simply asked if anyone had any ideas for the treatment of porokeratoses in May 2009.4 The lesion was first named by his grandfather, Marvin Steinberg, DPM, the “Father of Podiatry.”
You always know there is not a perfect answer for a treatment when so many suggestions are offered. Dermatology experts believe preparation of the remaining tissue after debridement is essential to long-term success.
Cryotherapy, such as that offered by the Cryoprobe™ (H&O Equipments) and delivered to the conical tissues that remain after debridement, seems to greatly delay the return of the lesion. Another popular treatment that offers a similar outcome is the placement of cantharidin (Canthacur, Paladin Laboratories), the medication developed from the blister beetle. It has been difficult to obtain at times over the past years. It was popularized some years ago as a treatment for verruca.
Both treatments produce an inflammatory reaction. Experts with whom I have spoken liken this to an immune reaction. This reaction, produced by the patient’s own body, is not yet understood completely but somehow delays the return of the lesion more than the solitary debridement technique.
A third treatment — the sublesional injection of 4% diluted alcohol solution proposed by Dr. Dockery — denies the lesion of its nerve supply. This results in subsequent deterioration of the lesion. This treatment may also speak to the fact that on occasion, after surgical treatment, I have found an associated neuroma beneath the dermatologic lesion.
There is a need for research on this old problem that still worries us and causes pain for our patients. However, we first need to settle on a name that fits this lesion. It is not a true porokeratosis like those associated with bronchial and squamous cell carcinoma or autosomal dominant polycystic kidney disease. To call the keratinized lesion we treat in the foot a “porokeratosis” is a true misnomer.
Dr. Satterfield is a Fellow and President-Elect of the American College of Foot and Ankle Orthopedics and Medicine. She is board certified in foot and ankle orthopedics and medicine. Dr. Satterfield is Director of the Pre-Clinical Curriculum and an Associate Professor at the Western University College of Podiatric Medicine in Pomona, Calif. She recently received the Master’s distinction from the American Professional Wound Care Association.
1. Personal communication with Brad Bakotic, DPM, DO.
2. Personal communication with Bryan Markinson, DPM.
3. Personal communication with G. “Dock” Dockery, DPM.
4. Available at http://www.podiatry.com/search/?search_text=porokeratosis&mode=all .
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3. Korstanje MJ, Vrints LW. Porokeratotic palmoplantar keratoderma discreta – a new entity or a variant of porokeratosis plantaris discreta? Clin Exp Dermatol. 1996; 21(6):451-3.
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7. Ujihara M, Hamanaka S, Hamanaka Y, Kamei T. A case of multiple eccrine porocarcinoma with stepping-stone distribution on the foot. J Dermatol. 1995; 22(6):450-7.
8. Jurecka W, Neumann RA, Knobler RM. Porokeratwoses: immunohistochemical, light and electron microscopic evaluation. J Am Acad Dermatol. 1991; 24(1):96-101.