Treating psoriasis with topical corticosteroids.

Topical corticosteroids (TC) are currently the standard local treatment for psoriasis, both as monotherapy or in addition to a systemic treatment. These are anti-inflammatory preparations for local use, composed of cortisone derivatives. They are particularly used for patients with a localised, moderate dermatosis, with spaced out flare-ups.

These medications are, on one hand, appreciated for their invisible and non-staining properties on the skin. On the other hand, they possess several useful properties in the management of psoriasis, notably immunoregulatory, anti-inflammatory, and antimitotic.

How do dermocorticoids act on psoriasis?

Applied topically, dermocorticoids help to soothe the skin by combating inflammation. They inhibit the NF-kB transcription factor by activating the transcription of the IkB gene, thereby conferring anti-inflammatory effects. Furthermore, glucocorticoids negatively regulate the expression of certain pro-inflammatory genes through transrepression, including cytokines, growth factors, adhesion molecules, nitric oxide, etc.

The quantity of dermocorticoids to be used is likely to fluctuate from one excipient to another, even for the same skin surface area. In essence, only one application per day should be adhered to. In the initial treatment of acute psoriasis, the frequency of applications is once or twice a day, for the first three days.

There is no need to increase the number of applications, due to the reservoir effect that occurs in the stratum corneum, capable of releasing the active substance applied to the skin for hours. Moreover, an increase in the dose used may cause tachyphylaxis, a phenomenon of rapid body tolerance to the medication. Furthermore, dermocorticoids should be used sparingly and with caution in young children due to their ability to cross into the bloodstream.

The use of dermocorticoids can be associated with various side effects.

• Skin atrophy.

  This is the most common side effect. It is caused by a reduction in the number and size of keratinocytes, leading to a thinning of the epidermis and revealing the vessels in the subcutaneous tissues.

• Tachyphylaxis.

  This refers to a phenomenon indicating the resistance capacity to a dermatosis, psoriasis, to treatment after prolonged and uninterrupted applications. It appears more rapidly when the corticosteroid is potent and, for the same molecule, the concentration is high.

• The Cushing's Syndrome.

  This refers to a syndrome that occurs following the intake of cortisol, leading to an excessive production of corticosteroids by the adrenal glands.

There are also other side effects such as diabetes, high blood pressure, gastric ulcers, etc.

Generally, there are a few contraindications to treatment with dermocorticoids.

• Infected skin lesions;

• Dermatoses that take time to heal under the effect of corticosteroids;

• Known allergies to dermocorticoids.

In instances of infected lesions or dermatoses, the use of topical corticosteroids could potentially exacerbate the situation by promoting the growth of microorganisms, particularly due to their pro-infectious potential. In cases of known allergies or hypersensitivity to topical corticosteroids, their use is contraindicated due to the risk of triggering skin reactions such as rashes or defensive reactions from the body.

Regarding psoriasis, dermocorticoids are contraindicated in cases of eruptive guttate psoriasis that extends over a large skin area. The same applies to nail psoriasis, which often resists treatment.

• KATZ H. I. Topical corticosteroids. Dermatologic Clinics (1995).

• CARTIER- EL HADRI C. Les dermocorticoïdes en pratique officinale. Sciences Pharmaceutiques (1996).

• UVA L. & al. Mechanisms of action of topical corticosteroids in psoriasis. International Journal of Endocrinology (2012).

• PILLON F. & al. Les traitements locaux du psoriasis. Actualités Pharmaceutiques (2015).