It might be easy to dismiss chronic skin conditions as mere cosmetic or quality-of-life issues–matters of inconvenience and self-consciousness. These are valid concerns in themselves, and they merit attention and treatment. Some skin conditions, though, have serious implications and demand immediate evaluation and treatment.
Disseminated superficial actinic porokeratosis (DSAP) is one such condition. It is characterized by flat or slightly-raised scaly lesions (keratoses) distributed over the arms and legs (disseminated), occurring most commonly in areas that have been exposed to sunlight or other sources of ultraviolet (UV) radiation. The lesions themselves are not cancerous, but DSAP is regarded as a precancerous condition because squamous cell carcinoma (skin cancer) can develop within the larger keratoses. For this reason, anyone with symptoms suggestive of DSAP should be evaluated immediately by a board-certified dermatologist.
Recognizing Disseminated Superficial Actinic Porokeratosis (DSAP)
Most of the skin cells–90%--in our outermost layer of skin, or epidermis, are keratinocytes. These cells originate in the lowermost layer of the skin, the stratum basale. From there they migrate to repair damage to the epidermis and to replace dead skin skills. Keratinocytes produce keratin–a tough, fibrous protein that becomes hardened (cornified) over time and sloughed away. This protein is crucial to the maintenance of the skin barrier.
Disseminated superficial actinic porokeratosis is a disorder of gene mutations in the pathway for the keratinocytes to make cholesterol. More specifically, it is one of the six variants of porokeratosis, disorders in which the keratinocytes proliferate at an abnormally high rate.
The disorder is often confused with actinic keratosis. The lesions caused by these disorders are similar and they both are associated with UV exposure. Actinic keratosis lesions, however, occur mostly on the face and the scalp, whereas DSAP lesions are mostly found on the arms and legs.
The lesions look like scaly, reddish brown ovals or circles with a thin, raised rim around their outer edges (this is called a 'coronoid lamella’). The spots are mostly found on the arms and legs, but they can also appear on other sun-damaged skin–they very rarely occur on the face. They may or may not itch, and itching tends to worsen with UV exposure. The lesions also tend to grow with UV exposure. They cause a red-and-brown mottled appearance to arms and legs, which can be unsightly.
Risk Factors With DSAP
By now, you might have deduced that sun exposure is a major risk factor for DSAP. While the disorder requires UV exposure to develop fully, it is a multifactorial disorder. Heredity, environment, and immune system function all figure into the development and progression of the disorder.
This disorder most frequently affects fair-skinned people of European descent. People with skin that does not tan and easily sunburns are at the greatest risk. It presents usually between the ages of 30 and 45, and it is seldom diagnosed before age thirty. It occurs more frequently in women than in men.
A familial form of DSAP is caused by a mutation on the MVK gene. This form of DSAP is an autosomal dominant trait; a parent with this mutation has a 50% chance of passing the trait on to their child. In addition to directing the production of cholesterol, the MVK gene plays a role in regulating the life cycle of keratinocytes. The mutation affects these cells’ ability to repair UV damage. Toxic levels of the precursors of cholesterol synthesis damage the skin. At the same time, there is a deficiency of cholesterol needed by healthy keratinocytes.
Other risk factors include infection and trauma to the skin. Organ transplant patients and those with illnesses that suppress the immune system are also at risk
Diagnosis and Treatment
Diagnosis begins with a visit to an experienced board-certified dermatologist. The dermatologist will examine the lesions visually, sometimes with the help of a specialized magnifier called a dermatoscope. They are looking for clues such as the coronoid lamellae, which is caused by abnormal proliferation of keratinocytes, as well as thinning (atrophy) of the skin tissue in the center of the lesion. These are hallmarks of porokeratosis.
The dermatologist might order a skin biopsy of lesions to confirm the diagnosis and to rule out malignancy. The biopsy will encompass both the inside of the lesion and its outer border, in addition to the skin beneath the lesion.
Changes in the lesions, especially increased redness, crusting or scaling, warrant a biopsy. The prognosis for DSAP is generally favorable, however, with fewer than 10% of patients developing malignancies.
There is no cure for DSAP. The lesions are the result of cumulative cellular damage occurring over years, well before visible lesions are formed. Because of that, it is difficult to predict where or when new lesions will occur. Treatment typically involves a multi-pronged approach, with a focus on supporting normal keratinization and inhibiting the proliferation of keratinocytes while managing discomfort. Most therapies are topical; DSAP does not readily respond to many systemic treatments.
Within the last few years, topical treatment with lovastatin has become the gold standard for treating DSAP. Lovastatin is a cholesterol-reducing drug that when used topically, blocks the buildup of toxic metabolites from mutated Cholesterol synthesis. When it's combined with the cholesterol that the skin needs for healthy keratinocytes, this has become the overwhelmingly most effective treatment of disfiguring DSAP. Within 4-6 weeks the improvement is usually dramatic. For residual redness and the few lesions which don't fade, board-certified dermatologist Steve Harlan has his patients use SmartLotionⓇ daily. Every morning his patients apply sunscreen, or they keep the arms and legs covered with clothing in the sun.
Topical Diclofenac is a nonsteroidal anti-inflammatory drug (NSAID) gel that was initially tried out for another variant porokeratosis. It is a safe drug for most people; it is better for inhibiting the formation of new lesions than in clearing existing lesions.
Oral vitamin D3 is prescribed to support the normal development of keratinocytes.
Chemotherapy drug Topical 5-fluorouracil (5-FU) inhibits abnormally rapid proliferation of keratinocytes. It can provoke severe inflammatory responses in some patients, causing symptoms such as redness, ulcerations, and skin irritation; these symptoms are normally short-lived.
Vitamin A derivatives called retinoids are applied to the skin to help remove abnormal skin cells and to promote the generation of healthy cells. Retinoids are not as effective as many other topical treatments. Oral retinoids are not effective in treating DSAP.
Beyond topical treatments, there are procedures a dermatologist might order to treat keratoses.
Cryotherapy involves spraying lesions with liquid nitrogen so that they can be removed and replaced with healthier keratinocytes.
Photodynamic therapy uses red or blue light to activate a drug called a photosensitizer that has been applied to the skin. Once activated, the photosensitizer generates reactive oxygen species (ROS), a subset of free radicals that attack abnormal cells.
Photodynamic therapy begins with the application of aminolaevulinic acid (ALA) or methyl aminolevulinate (MAL) to the skin. The drug is then allowed to incubate for a period of time determined by the dermatologist based upon the extent and severity of the lesions. Incubation periods typically range from 80 minutes to four hours. After incubation, the patient sits in front of a special light for several minutes. After therapy, the skin might be red, and it may peel. It will also be more sensitive to light, so patients are instructed to avoid sun exposure for 48 hours. Treatments are effective at treating existing lesions, but they usually must be repeated for the emergence of new lesions.
Your doctor might also use lasers to target lesions. These procedures are often effective at treating existing lesions, but they are expensive and impractical for widely-disseminated lesions.
Living with DSAP
Treating DSAP can feel like an exasperating game of whack-a-mole. The best treatments cannot prevent all future outbreaks. Patients can support their treatments by avoiding sun exposure or other sources of UV radiation (including tanning beds, fingernail polish dryers, and craft lamps used for curing resins).
Some dermatologists recommend using sunscreen in addition to covering the skin. This means that sunscreen is applied even when the skin is covered when exposure to sunlight is expected, including times spent in cars or in rooms that receive a lot of natural light.
Moisturizers support the health of the skin barrier, and they also reduce the discomfort caused by dry, scaly lesions. Patients with DSAP should moisturize at least twice a day. Many people with active skin conditions find that creams or ointments work better for them than water-based lotions.
You should monitor your skin for changes to existing lesions such as redness, scabbing, or irregular borders. Promptly report these changes to your dermatologist.
SmartLotion®, briefly mentioned earlier, is an excellent adjunctive to DSAP treatments. This over-the-counter cream helps with residual itching and redness, and it does not interfere with prescription treatments (consult your dermatologist before you add it to your treatment! Make no changes to your regimen without a physician’s supervision). It also helps with irritation that commonly occurs with topical retinoids and topical 5-FU treatments.
Because SmartLotion®’s prebiotic formula promotes a healthy skin barrier, it can effectively use a lower dose of hydrocortisone (0.75%) than most creams. This allows it to address itching and redness without the risk of skin atrophy or topical steroid withdrawal (TSW).
SmartLotion® was created by Dr. Steve Harlan, a board-certified dermatologist, to safely treat patients with chronic, recurring skin disorders (like DSAP). He formulated SmartLotion® so that these patients could find relief from their symptoms without the risk of side-effects, regardless of the maintenance schedule they require.
For the treatment of DSAP-related dermatitis, Dr. Harlan normally instructs his adult patients to apply SmartLotion® two times a day for up to two weeks.
If the patient responds well to the treatment, he usually has them taper down to one application a day for the next two weeks. The rate of tapering is determined by how quickly the skin heals–this means that it varies from patient to patient.
If there is no improvement within the first two weeks, Dr.Harlan prescribes a three-week course of a stronger treatment. Once the symptoms are under control, he has them switch back to SmartLotion®.
After initial control and tapering, Dr. Harlan recommends his patients adopt a long term routine that works for them. He usually recommends applying SmartLotion® once a day or less, as needed–some patients need a daily application, while others only require three applications a week. Patients should moisturize at least twice a day, he says, especially if there are active lesions.
Dr. Harlan emphasizes the importance of seeing a dermatologist for active keratoses; he always does a skin cancer check if there are active DSAP lesions.
His typical treatment for keratosis lesions is 5-Fluorouracil cream or cryotherapy.
The outlook for patients with DSAP is optimistic, overall. However, it’s a disorder that requires proactive management; patients must protect themselves from unnecessary UV exposure, and they must always keep an eye on new or worsening lesions. Patients can position themselves for success by consulting an experienced physician, moisturizing frequently, and avoiding UV exposure. SmartLotion® is another invaluable tool for managing DSAP symptoms. If you suffer from DSAP, talk to your dermatologist about adding it to your treatment.
If you've learnt from or enjoyed our article on DSAP, check our our blog for more eczema-related insights.
Steven Harlan MD
Board Certified Dermatologist
Inventor of SmartLotion®