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Actinic keratoses (AKs) are also called solar keratoses because they are caused by years of sun exposure. These skin lesions are precancerous, which means they have the potential to convert to skin cancer.
What causes actinic keratoses (AKs)?
The ultraviolet radiation (UVR) from the sun or indoor tanning gets absorbed by the endogenous chromophores present in the skin cells (keratinocytes such as DNA, melanins, and amino acids) and damages these structures to produce free oxygen radicals. These unstable molecules wreak havoc on other nearby cellular structures.
Once the DNA is damaged, it will cause permanent instability to the natural keratinocyte function, leading to precancerous and cancerous states.
An example of an exogenous (outside the body) chromophore is sunscreen as it is meant to absorb the UVR to protect the skin from outside the body. (1)
Where are actinic keratoses found?
As AKs are related to chronic sun damage, they are predominantly found in the typically exposed areas of the skin that get the most sun, such as the face, scalp, ears, arms and hands, and lower legs (more frequently in women).
AKs can also occur on the lips with the same scaling quality, but when on the lips, this condition is called actinic cheilitis.
What are the symptoms of actinic keratoses?
Most AKs are:
- They can range in size from very small to approximately the size of a quarter.
- The color can range from skin-colored to white, red, silvery, or brown, but a common feature is the rough scaling texture.
- Some AKs can rapidly grow upward with a firm horn-like structure and are appropriately named “cutaneous horns.” (2)
What are the treatment options for AKs?
The treatment for AKs is divided into:
a. Pinpoint (or lesion-directed) destruction
Lesion-directed therapy consists of the destruction of the AK by cryotherapy with liquid nitrogen and is better suited for fewer (<10) lesions.
The application of cryotherapy will turn the skin red for the first 24 hours, and then a blister will form. This inflammatory reaction and subsequent healing are thought to treat the AK.
Risks of this procedure include pain, edema, infection, and permanent skin discoloration.
b. Field therapy (cream and/or light therapy)
There are many different types of field therapy:
- 5-FU cream
- Imiquimod cream
- Ingenol mebutate gel
- Photodynamic therapy (PDT)
There is no current agreement on the best field treatment for AKs. Each product comes with its own side effects which can vary from patient to patient, but generally include redness, pain, itching, irritation, flaking, and scaling.
Moreover, patients need to discuss the appropriate application method with their doctor before starting treatment as each of these products has its own recommended application frequency and duration.
How is actinic keratoses diagnosed?
Because AKs are often light or skin-colored, they are not very noticeable and hard to diagnose through visual inspection. Instead, AKs are usually diagnosed by feeling the skin due to their rough texture.
AKs may be asymptomatic, but can sometimes be itchy or painful with a raw feeling. These lesions can often resurface in the same spot after clearing. (3)
Can actinic keratoses be cured without any medical intervention?
Sort of. Information on the regression, resolution, and recurrence of AKs differs from study to study. The common theme is that the majority will regress, but there is varying opinion on the recurrence rate.
One of the leading large research studies in AKs found that the majority of AKs regress, and at the end of 5 years, 70% were no longer present. (4)
Another report claimed that at least 50% spontaneously regress. However, regressed lesions often reappear. (9)
What home remedies can be used to treat AKs?
The following home remedies have become popular for the management of actinic keratoses, but their efficacy is only supported by anecdotal evidence rather than scientific research:
1. Apple cider vinegar: Apple cider vinegar is well documented to have both antimicrobial and antifungal properties. (6) I have only seen anecdotal evidence for using apple cider vinegar for the treatment of AKs. The acetic acid is thought to treat the AKs by possibly interfering with cytokine and protein production.
2. Coconut oil: Coconut oil, while a good moisturizer for non-acne skin, only has anecdotal evidence of treating AKs. Its mechanism is unclear.
3. Green tea: Green tea (oral and topical) and tea tree oil have been reported to be of benefit, but again, only anecdotally. Several plant extracts have been tested in the treatment of AKs. Overall, the results have been lackluster, although two extracts did stand out as having some beneficial effects: birch bark and petty spurge.
- Birch bark was found to be more efficacious if used in the early treatment of AKs and, in fact, was found to be as effective as cryotherapy when treating lower-grade AKs. (5)
- Petty spurge (also known as milkweed) contains ingenol mebutate. Studies using this product found it to be highly effective against AKs compared to placebo, and scar formation was not noted. These studies were later confirmed in a double-blind, placebo-controlled study, and this gel was approved as a prescription drug in 2013. (7)
Are AKs a common condition?
AKs are a common dermatologic condition, being diagnosed at >10% of dermatology visits with over $1 billion in annual costs.
They are not usually found in children or young adults, but in middle-aged and older adults as it is a condition related to chronic sun exposure.
What is the difference between actinic keratoses and seborrheic keratoses?
AKs are considered a precancerous condition, whereas seborrheic keratoses are common benign skin lesions.
Seborrheic keratoses are typically found in older adults, which is why they were once called senile keratoses but the dermatological community did away with this terminology as it implied mental weakness as well.
Seborrheic keratoses are brown, grey, and white in color and tend to have a warty or “stuck-on” appearance. These lesions do not have malignant potential, but patients do tend to get more lesions with increased age.
Is actinic keratoses a cancerous condition?
No, AKs are a precancerous rather than a cancerous condition. AKs may regress, stay stable, or turn cancerous.
If they progress to skin cancer, they are the keratinocyte derivation of squamous cell carcinomas or basal cell carcinomas.