What parts of the body does psoriasis affect?

What is psoriasis?

Psoriasis is a chronic, recurrent inflammatory disease affecting the skin, with possible systemic repercussions, mainly at the joint level in the form of psoriatic arthropathy. According to prevalence data, it can affect 0.5-5% of the general population depending on the country. In Spain, the prevalence is around 2% of the population. It can begin at any age, from childhood to senescence. The clinical manifestations of psoriasis are very varied, with the most characteristic expression being the presence of symmetrical erythematous scaly plaques with well-defined borders, preferentially located on the extensor surface of the extremities and scalp. It is a disease with a multifactorial cause, since it involves the combined action of numerous genes and a series of triggering factors such as physical or emotional stress or certain infectious processes, the most characteristic of which is pharyngotonsillitis.

What are the types of psoriasis?

There is a tendency to think that there is only one type of psoriasis, when the truth is that there are different forms of presentation.

1. Plaque psoriasis: This is the most common form and affects approximately 80% of people with psoriasis. It can appear on any part of the body but usually on the elbows, knees, back, navel and scalp.
2. Psoriasis on the scalp: It affects 50-80% of people with psoriasis. The symptoms are the same as for plaque psoriasis. Scalp psoriasis can range from very mild, with slight scaling not adhering to the scalp to severe forms with thick plaques covering the entire scalp, extending beyond the hairline to the forehead, nape of the neck and around the ears.
3. Guttate psoriasis: This type affects approximately 10% of people with psoriasis, mostly children and adolescents. It appears as small red scaly spots that look like water droplets splashed on the body. Guttate psoriasis is often triggered by a strep throat infection. In mild cases, it may disappear without treatment. Guttate psoriasis may develop into plaque psoriasis (the most common form of psoriasis).
4. Pustular psoriasis: It can manifest itself in localized or generalized form, the latter being severe and sometimes requiring hospitalization for management and control. It affects less than 5% of people with psoriasis. It may appear as a complication of plaque psoriasis after taking certain medications or after abruptly interrupting treatment that had been used continuously for a long period of time.
5. Flexural or inverted psoriasis: Less common, this form of psoriasis usually appears in folded areas such as the armpits, groin, submammary area or genital area. It appears as intense red plaques around the skin folds, and cracks may appear at the edges. Given its location, it can be aggravated by sweating and skin rubbing, and lead to superinfection by fungi, the most frequent of which is candidiasis.
6. Erythrodermic psoriasis: Occurs in very few cases. It is defined as psoriasis affecting more than 90% of the body surface. It is one of the most severe forms of psoriasis and can be life-threatening as it affects the skin’s protective barrier.

What causes psoriasis?

As mentioned above, psoriasis is a multifactorial disease, with a predisposing genetic basis and environmental triggers. Among the triggering factors, the most frequent are:

1. Stress: Very frequent and easily controlled by the patient himself.
2. Trauma: A direct blow to the skin can trigger psoriasis lesions in the affected area. This effect is known as Koebner’s phenomenon and appears in 1 out of 4 patients. Other types of trauma such as sunburn, post-operative scars, recent tattoos or drug eruptions can also cause psoriasis lesions to appear.
3. Bacterial or viral infections: can induce or worsen psoriasis lesions by activating immune system cells.
4. Medications: Some medications may contribute to flare-ups. It is therefore important to inform the physician of all medications the patient is taking.
5. Weather: Cold weather and seasonal changes can trigger psoriasis flare-ups.
6. Other: Alcohol, smoking and obesity have been closely linked to psoriasis outbreaks.

Is psoriasis contagious?

No. Many people believe that psoriasis is infectious or contagious. Psoriasis is an inflammatory, non-infectious disease. It is not transmitted between patients and is therefore not contagious.

Can it be prevented?

Since psoriasis is a disease of multifactorial origin, there will be factors on which we can act and prevent, such as avoiding smoking, unnecessary trauma such as tattoos or alcohol abuse. But there are other factors that are difficult to control, such as infections or stress.

Some medications, such as lithium, beta-blockers and some anti-malarial tablets, can worsen psoriasis. It is therefore important to inform your doctor of any medication you are taking.

Stress is also thought to be a trigger for psoriasis, so it is advisable to eat a balanced diet, exercise regularly and avoid stressful situations. It is also helpful to wear light clothing made of fabrics that do not irritate the skin or cause itching.

What is the treatment?

In general, treatments for psoriasis fall into three main areas:

1. Non-systemic therapies:
   1. Topical therapies: Treatments used externally and applied locally on lesions.
   2. Phototherapy: Ultraviolet light therapies, usually narrow band ultraviolet B.
2. Systemic therapies: Medications administered as tablets or injections that help control inflammation.
3. Biological therapies: Drugs made from human or humanized cells that act on the immune system. These drugs are given as subcutaneous injections or intravenous infusions.

For more information on psoriasis and its treatment contact a specialist in Dermatology.