Laser treatment for eliminating psoriasis?

The psoriasis is a skin disease that is identified by red and scaly patches that cover specific parts of the body. These can be a source of itching and irritation, their intensity varying from one individual to another. They appear following skin inflammation caused by a failure of the immune system.

T lymphocytes produce inflammatory molecules (IL-17, IL-22, TNF-α, etc.). These molecules stimulate the proliferation of keratinocytes. The renewal period of these cells, normally three weeks, is then reduced to three days. This results in an accumulation of immature keratinocytes on the skin's surface, increasing the thickness of the outer layer (the cornea).

The phototherapy based on UV radiation has proven its effectiveness in treating psoriasis. However, new methods such as lasers have emerged and also help to alleviate the symptoms of psoriasis.

The term "excimer" originates from the combination of the words "excited dimer" and refers to a temporary excited state that forms when noble gas molecules, such as argon or krypton, bind to halogen molecules like fluorine or chlorine. This phenomenon is characterised by high energy and is utilised in excimer laser technology.

The excimer laser has been adapted for the treatment of psoriasis using a specific wavelength of 308 nm, which allows it to effectively penetrate the upper layers of the skin, where psoriasis lesions are located. This wavelength has demonstrated efficacy in the treatment of plaque psoriasis.

A study conducted on 10 patients suffering from psoriasis were treated with a 308 nm excimer laser at a frequency of three times per week until the skin disease disappeared. On average, the patients underwent 8 sessions. This treatment allowed the psoriasis plaques to disappear three times faster than with the UVB phototherapy.

Thanks to its wavelength of approximately 595 nm, this laser specifically targets red blood vessels by promoting optimal absorption of oxyhaemoglobin, a combination of haemoglobin with oxygen. The light emitted by the laser is absorbed by the oxyhaemoglobin present in the blood of the vessels, allowing for the effective treatment of all blood vessels involved in the lesions in question. The energy of the light radiation is converted into heat to weaken the walls of the capillaries. This allows for the selective targeting and destruction of the specific vessels that one wishes to treat.

An epidermal cooling stage is necessary to prevent skin burns. Often, the laser is coupled with a cooling system. The size of the impacts and the pulse durations are variable. Generally, the shorter the pulse duration, the more it will act on fine blood vessels. The longer the pulse duration, the more effective it can be on telangiectasias. One or more sessions may be necessary depending on the lesions. Sometimes, bruises or purpuras may appear after this type of treatment but they eventually disappear on their own.

This type of treatment has proven effective for nail psoriasis and specifically for lesions of the nail bed, particularly onycholysis and subungual hyperkeratosis.

CO2 lasers are ablative lasers that utilise carbon dioxide. This laser is capable of emitting infrared radiation with a wavelength of 10,600 nanometres. Its operation is based on the excitation of carbon dioxide molecules. This laser has been used in dermatology since the 1990s.

In 1985, this technique experienced success on three patients suffering from plaque psoriasis. Furthermore, it was reported that the treated areas did not experience psoriasis for three and a half years. Although the CO2 laser has demonstrated its effectiveness in dermatological procedures and the treatment of certain skin conditions, its specific use for the treatment of psoriasis has not been the subject of scientific studies or widespread approvals. Thus, it does not constitute a primary treatment for psoriasis.

• ALORA M. B. & al. CO2 laser resurfacing of psoriatic plaques: a pilot study. Lasers in Surgery and Medicine (1998).

• MORDON S. Le traitement du psoriasis par laser excimere. Réalités Thérapeutiques en Dermato-Vénérologie (2000).