Chronic disease with an origin due to a hyperactivity of the immune system that mainly affects the skin and nails. It usually involves periods in which there are no or mild symptoms, followed by others in which they are more severe and can greatly affect the quality of life. It is a common disorder for which a worldwide prevalence of around 2-3% has been estimated.
The new skin cells generated by the organism ascend from the deep layers of the skin to the most superficial layers where the older cells are being shed. This process, which occurs in normal conditions in a maximum of 4 weeks, in psoriasis is accelerated to 3-7 days, so that the immature cells accumulate in the superficial layers of the skin causing the associated symptoms.
The immune system seems to be responsible for this accelerated turnover as it directs its response against healthy skin cells, which triggers healthy skin cells to be produced at a faster rate. The exact cause of this activation of the immune system is unknown, however, in addition to the genetic contribution, several triggers or risk factors that initiate outbreaks have been described:
- Skin lesions, cuts, scratches, insect bites, sunburns.
- Skin infections, respiratory infections, otitis, bronchitis or throat infections specifically due to streptococcus.
- Weather, especially cold and dryness.
- Excessive alcohol consumption.
- Smoking and passive exposure to tobacco smoke.
- Hormonal changes, especially in women, during puberty and menopause.
- Certain drugs: lithium, antimalarials (chloroquine), antihypertensives (enalapril, propranolol), antiarrhythmics (quinidine), anti-inflammatory drugs (ibuprofen, indomethacin). Also rapid withdrawal of oral or systemic corticosteroids.
- Concomitant presence of other immune disorders.
Psoriasis is a multifactorial genetic disease for which genetic factors explain about 70% of disease susceptibility. The largest meta-analysis of GWAS association studies performed for psoriasis to date on nearly 12,000 cases and more than 200,000 controls has provided an outline of the genetic architecture of common psoriasis variants identifying 55 association loci for psoriasis.The largest meta-analysis of GWAS association studies for psoriasis to date on nearly 12,000 cases and over 200,000 controls has provided an outline of the genetic architecture of common psoriasis variants identifying 55 susceptibility loci highlighting interferon and NFκB signaling pathways, and regulatory elements of different T-cell subtypes.
Symptoms usually appear between 15 and 35 years of age, although it can also affect children and older people. There are several types of psoriasis, plaque psoriasis or vulgaris, the most common that mainly affects the skin, scalp psoriasis, psoriasis of the nails, psoriasis in drops sometimes triggered after streptococcal throat infections, inverse psoriasis that mainly affects the inguinal folds, buttocks and breasts, pustular psoriasis and erythrodermic psoriasis. In addition, there is another entity related to psoriasis that affects the joints known as psoriatic arthritis.
Most types of psoriasis have cycles, with flares lasting weeks or months and then subsiding or even going into remission. Signs and symptoms that can vary from person to person, but among the most common depending on the type include:
- Reddish patches of skin covered with thick, silvery scales.
- Small scaly spots.
- Dry, cracked skin that may bleed or itch.
- Itching, burning or irritation.
- Thickened, pitted or grooved nails.
- Swollen and stiff joints.
The most commonly affected areas are the lower back, elbows, knees, legs, soles of the feet, scalp, face and palms of the hands.
Although the causes that trigger psoriasis outbreaks are unknown, certain measures can be taken to reduce symptoms or even outbreaks:
- Keep the skin moisturized using preferably thick creams and lotions, or topicals in case of the scalp. To help remove the scales, apply cream on them and then cover the area with plastic or other impermeable material. Leave it on for a few hours and then remove it. Another alternative is to use humidifiers at home.
- Maintain skin hygiene to treat the development of skin infections.
- Avoid dry and cold weather as much as possible.
- Maintain a healthy weight by doing regular physical exercise and maintaining a balanced diet rich in fruits and vegetables.
- Quit smoking and avoid areas laden with tobacco smoke.
- Avoid stress.
- Moderate alcohol consumption.
- Limiting skin exposure to sunlight.
It is important to try to identify the factors that trigger psoriasis outbreaks in each person specifically in order to avoid them.
13.5 million variants
Tsoi LC et al.Large scale meta-analysis characterizes genetic architecture for common psoriasis associated variants. Nature Communications. 2017 May;8:15382.