Symptoms
Actinic keratosis is a skin disease that manifests itself in various forms. Pink or brown, scaly, highly keratinized patches or papules often form on a reddened base, with sizes ranging from millimeters to centimeters. The lesions can occur all over the body, but usually affect sun-exposed areas such as the head, bald head, ears, neckline, neck, extremities and backs of hands. On the lower lip, it is referred to as actinic cheilitis. An actinic keratosis is an initial squamous cell carcinoma that over time can develop into a dangerous, spreading and metastatic carcinoma. Today, the disease is considered a tumor and not merely a precancerous condition. It is therefore more technically correct to refer to it as “initial spinocellular carcinoma.”
Causes
Underlying is a proliferation of atypical keratinocytes in the epidermis. The main cause is considered to be chronic or cumulative irradiation with UV light, especially sunlight (actinic means radiation-induced). This leads to mutation of skin cells, for example in the telomerase gene and in the tumor suppressor gene, and additionally weakens the immune system locally. Risk factors include:
- Outdoor occupation, e.g. farmers, fishermen, construction site workers.
- Frequent sunburn
- Increased age
- Immunosuppression
- Light skin type (fair skin, blue eyes).
- Reduced pigmentation, eg albinism, heredity.
- Male gender
- Chemicals and medications: Arsenic, immunosuppressants, photosensitizing agents and drugs, tar.
- Geographic localization, e.g. Australia, proximity to the equator.
- Human papillomavirus (controversial).
Diagnosis
Diagnosis is made in dermatological treatment based on physical examination and with tissue sampling. In the process, similar skin diseases must be excluded.
Prevention
For prevention, good sun protection with the appropriate measures is recommended. In particular, high-risk groups must protect themselves well, for example, immunosuppressed persons or people who regularly spend long periods of time outdoors:
- Avoid direct sunlight, especially between 11 am to 3 pm.
- Wear protective clothing: headgear with neck protection, long sleeves and pants, special clothing with UV protection.
- Sunscreen (UV filter) with a protection factor adapted to the skin type. For risk groups, for example, the specially developed medical product Daylong actinica is available.
- From a solarium visit is in any case not recommended.
Treatment
Therapy is necessary because it is not yet possible to predict exactly which lesions will develop further. The corresponding skin sites are removed or destroyed in medical treatment with various procedures. These include icing with liquid nitrogen (cryotherapy), curettage, excision, dermabrasion, laser, radio or phototherapy (e.g. 5-aminolevulinic acid) and cauterization, for example with trichloroacetic acid. Drugs used include: 5-fluorouracil (Efudix 5%, Actikerall 0.5%) is a cytostatic drug that interferes with DNA and RNA synthesis. It is applied locally as an ointment or solution and causes a strong inflammatory reaction, ulceration, and eventual cell death and healing. The treatment lasts about 2-8 weeks, depending on the regimen. A disadvantage is the unpleasant local side effects. There are suggestions how to reduce them, e.g. with the lower concentration of 0.5%. The corresponding drug was approved in many countries in April 2011 (Actikerall). Imiquimod (Aldara, Zyclara) is an immunomodulator approved for treatment in the form of a cream. It activates the immune system and promotes the synthesis of cytokines, which have antitumor activity. This leads to an inflammatory response and eventual healing. Diclofenac gel 3% (Solaraze, generic) was approved in many countries in 2010. Inhibition of cyclooxygenase probably inhibits vascularization (angiogenesis). The gel is generally well tolerated, unlike the other drugs, but requires a longer treatment period of more than 2 to 3 months. Methylaminolevulinate (Metvix) is used as part of photodynamic therapy.It accumulates in tumor cells and reacts with the supplied red light to form reactive radicals that lead to local cell destruction. 5-Aminolevulinic acid is also used. Oral retinoids such as isotretinoin (Roaccutane, generics) or acitretin are also used in combination with topical 5-fluorouracil, but are not approved by authorities in many countries for this indication. Ingenol mebutate (Picato, off label) is a cytotoxic ingredient derived from the milky sap of garden spurge . It was approved as a gel for treatment in many countries in 2013. In 2020, the approval was revoked.