A 51-year-old man presents to the clinic with a chief complaint of multiple warts on both lower legs and feet. He reports that the lesions have been present for almost two years and appear to be increasing in numbers and size. The patient saw his family physician a year ago and was told to begin treating the warts with an over-the-counter wart medication containing a low percentage of salicylic acid. Since that time, he has randomly applied the wart cream with little success but did note that some of the lesions appeared to get smaller with treatment.
Approximately three months ago, the patient saw another physician who treated some of the larger lesions with topical liquid nitrogen. The patient stated that the lesions got red, blistered and then resolved. However, he said the skin area remained dark in color until just recently. With further questioning, the patient stated he had no known exposure to any chemicals, paints, toxins, irritants or other potential allergens, and was taking no medications, vitamins or supplements. The patient also had no known allergies to any medications or environmental agents. No one else in his household or within his family had any similar skin conditions.
The physical examination revealed a large number of epidermal white-to-gray warty papules on both of the patient’s feet and lower legs. The lesions appear to change in appearance and increase in numbers as one looks down the leg toward the feet. The lesions became thicker, whiter and larger, especially on the lateral ankle and foot area. The lesions ranged from 2 to 4 mm in diameter.
There were no skin color changes or edema, and none of the lesions were symptomatic. Careful examination found no other similar appearing lesions on the upper extremities or torso region. There were no other obvious dermatological
findings other than the ones noted on the initial examination and the remainder of the physical examination was without any positive findings.
A Closer Look At Stucco Keratoses
Stucco keratoses are asymptomatic benign acquired papular warty skin lesions that usually occur on the distal parts of the lower limbs in men greater than 40 years of age. However, they may appear at any age on any other body part and one may see these with females as well.
The lesions may range from 1 to 10 mm in diameter and may be white, gray or light tan in color. Their true nature and pathogenesis are not well understood. The name stucco keratosis is derived from the “stuck on” appearance of the lesions. Some authorities believe that stucco keratoses are a variant of seborrheic keratoses. They are not associated with any syndromes and there is no clear association with human papillomavirus (HPV).
Most patients report a history of prolonged or severe solar exposure but the relationship of this to the development of the lesions is uncertain. Surface friction may contribute to the development of the lesions and they are thought to increase in number and prominence farther down the leg because these areas of the body produce less sebum. It has been estimated that stucco keratosis affects 20 percent of the United States population and it is found in all races.
One would make this diagnosis via clinical findings. The podiatrist should perform a shave biopsy on lesions that do not scrape off easily or have unusual colors or appearance, and on any lesions that spontaneously crack and bleed.
What To Consider In The Differential Diagnosis
Stucco keratosis is far more common, drier and more papular than flat warts. They are easy to remove and do not bleed when one scrapes them off. They affect a much older patient population than warts do.
Seborrheic keratoses are usually less dry, firm, more pigmented and are more difficult to scrape off than stucco keratoses. Actinic keratoses are relatively uncommon on the lower legs and feet, and are not as dry and warty as stucco keratoses.
Xerosis (dry skin) is much more uniform in nature and does not typically have distinct areas of raised, dry, papular lesions. Dermatofibroma is an incorrect diagnosis because these lesions are by nature firm, pigmented, compact and intradermal rather than epidermal. They are also much more likely to be solitary than stucco keratoses.
One would make the diagnosis of acrokeratosis verruciformis or epidermodysplasia verruciformis via biopsy and they are easy to distinguish from stucco keratosis through the dermatopathology findings.
Essential Keys To Prevention And Treatment
Prevention of stucco keratosis is one of vigilance with hygiene, regular bathing and using moisturizers immediately after bathing. Protection from excessive solar exposure is also considered to be a preventative measure.
In regard to problematic stucco keratosis, one could consider treatment with cryotherapy, curettage, topical urea, topical lactic acid or topical imiquimod 5% cream (Aldara, 3M). In many cases, no treatment is necessary.
Cryotherapy is a very acceptable method of removing stucco keratoses but it may be a somewhat arduous process when numerous lesions are present. I prefer to use the CryoProbe™ unit (CryoSurgical Concepts) for benign skin lesions and this treatment is painless for most patients. Depending upon the thickness of the lesion, two freeze cycles of 10 seconds are usually required. The lesions may blister and then fall off in a few days. If any lesions remain, one may repeat the process. Clinicians may also use liquid nitrogen, either a spray or dipstick method, but it is much more painful. It is also common to see residual pigmentary changes following the removal of stucco keratoses with liquid nitrogen. The discoloration may remain for many months following treatment.
Podiatrists may also remove stucco keratoses by curettage and one can gently scrape off the lesions. After removing the lesions, one can apply a topical antibiotic until the area heals. Many patients complain that the curettage process is very uncomfortable and are less agreeable to this type of treatment as compared to cryotherapy.
One method of treatment is the use of bathing with a loofah sponge to remove much of the superficial stucco lesions. Then patients can follow this with daily application of lotion containing urea (Keralac® 35% lotion, Doak Dermatologics) or lotion with lactic acid (Lactinol® 10%, Pedinol).
Imiquimod 5% cream is reportedly useful in removing multiple lesions of stucco keratosis. One would apply the cream sparingly to each lesion three times a week for eight to 12 weeks. No cover is applied during treatment. This form of treatment is relatively expensive when compared to the other treatments, and may not have any benefits in the long run.
In summary, stucco keratoses are benign lesions, similar to seborrheic keratoses, which may be mistaken for warts on the lower extremities. Clinicians can remove them via cryotherapy, curettage or appropriate skin hygiene techniques. While these lesions are benign, clinicians should encourage patients to have a periodic skin examination in order to prevent missing other, more serious skin conditions that may occur concomitantly in the same areas.
Dr. Dockery is a Fellow of the American College of Foot and Ankle Surgeons, and a Fellow of the American Society of Podiatric Dermatology. He is
board certified in foot and ankle surgery. He is the Chairman of the Board and Director of Scientific Affairs for Northwest Podiatric Foundation for Education and Research.
Dr. Dockery is the author of Cutaneous Disorders of the Lower Extremity (Saunders, 1997) and Lower Extremity Soft Tissue & Cutaneous Plastic Surgery (Elsevier Science, 2006).
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