Stucco keratosis (SK) is a common, non-cancerous skin growth that typically affects older adults. It is classified as a benign papular lesion, resulting from an acquired, focal abnormality in the skin’s keratinization process that causes a buildup of the protein keratin. Since SK is harmless and does not pose a risk of malignancy, treatment is usually pursued for cosmetic reasons, as the growths are generally asymptomatic. This article will explain the characteristic appearance of SK, explore the factors thought to contribute to its development, and detail the procedures used for its management.
Distinctive Clinical Features
Stucco keratosis lesions have a specific look, often described as having a “stuck-on” appearance, similar to how plaster or stucco adheres to a wall. These growths are generally small, typically measuring between 1 and 4 millimeters in diameter, though they can sometimes reach up to 10 millimeters. The growths present as numerous, flat-topped papules with borders that can be round, oval, or slightly irregular.
The color of the lesions is usually white, cream, or grey, but a pale yellow or pinkish hue may also be observed. A defining characteristic is the dry, rough, and warty texture of the surface, which is caused by the accumulation of excess keratin. The scaly surface of the lesion can often be gently scraped or flicked off, leaving behind a smooth, dry surface that does not bleed.
Stucco keratosis most frequently appears symmetrically on the distal lower extremities, especially around the ankles, feet, and lower legs. It can also be found on the extensor surfaces of the forearms and the back of the hands. Lesions can range in number from just a few to several hundred, but they typically do not cause pain or itching.
Primary Contributing Factors
The development of stucco keratosis is strongly associated with the natural aging process, primarily affecting fair-skinned individuals over the age of 40. The peak incidence is often observed between the ages of 40 and 60. It is notably more common in males, who are estimated to be four times more likely to be affected than females, suggesting that changes in skin cell turnover over time are involved.
Chronic exposure to the sun’s ultraviolet (UV) radiation is considered a significant factor. Many affected people have a history of prolonged sun exposure, which can cause cumulative damage to skin cell DNA and contribute to the abnormal growth pattern. However, the exact role of UV damage is complicated by the fact that lesions do not always appear solely on the most sun-exposed areas.
Stucco keratosis is a type of hyperkeratosis, which involves the thickening of the outermost layer of the skin, the stratum corneum. Mechanical trauma or surface friction, such as repeated rubbing on the lower legs, is thought to be a contributing element. Genetic factors may also play a role, and research has linked the presence of certain types of human papillomavirus (HPV) infection in a subset of the lesions.
Treatment and Removal Procedures
Since stucco keratosis is a benign condition, treatment is primarily sought for cosmetic improvement or if the lesions become irritated. Recurrence following removal is a known possibility, and no single treatment method is universally effective. Dermatologists offer a range of non-invasive or minimally invasive procedures to manage the growths.
Physical Removal Methods
One of the most common physical removal methods is cryotherapy, which involves freezing the lesions with liquid nitrogen. This procedure causes the lesions to blister and fall off within a few days, and it may require two short freeze cycles for thicker growths. Another frequent approach is curettage, the gentle scraping or shaving of the lesions using a sharp instrument.
Curettage is sometimes followed by electrodesiccation, a technique that uses a high-frequency electric current to dry out any remaining tissue and control minor bleeding. For isolated lesions of cosmetic concern, shave excision can be performed, which removes the growth at the skin’s surface without needing sutures.
Topical Treatments
Topical treatments are also used, particularly for managing numerous or widespread lesions. Keratolytic agents, such as creams containing salicylic acid or urea, work to soften and exfoliate the thickened skin over time. Topical retinoids or a prescription cream like 5% imiquimod have been used, especially when HPV is suspected. These topical applications can also be used following a physical removal procedure to help reduce the chance of recurrence.