Introduction
Psoriasis is a serious non-communicable and chronic inflammatory skin disease that involves genetics, environmental factors, and immune system deregulation. It affects around 2-4% of the world’s population, and its prevalence has been increasing in recent decades, which has led the World Health Organization to consider psoriasis a global public health burden.
It has been established that the prevalence of the disease varies in different groups, with Caucasian and Scandinavian people being more affected than Asian and African people. It affects both females and males equally, and it more commonly affects adults, with two peaks of age occurrences – between 20 and 30 years of age and between 50 and 60 years of age. 1-5
The condition most often affects the skin – usually the scalp, back, elbows, and knees – but it can cause lesions in any part of the body. Additionally, around one-third of people with psoriasis also suffer from an involvement of the disease in the joints and develop psoriatic arthritis.
Psoriasis usually occurs in cycles, with intervals of weeks or months of symptoms that vary from mild to severe. Its symptoms can significantly impair people’s quality of life and people that have psoriasis have a higher risk of suffering from depression, diabetes, and cardiovascular diseases compared to those people who do not have psoriasis. Even though currently there is no cure for psoriasis, there are several highly effective treatments available. 1-5
What is psoriasis?
Psoriasis is a non-communicable skin disease that has a strong genetic component, with several genes playing an important role in disease development. Additionally, there are many environmental factors that are well-established as triggers for psoriasis, such as skin injuries, respiratory infections, use of certain medications, weather conditions, smoking, and alcohol consumption. Lastly, the disease involves the deregulation of the immune system, including an overactivation of the immune cells. 1-5
What are the symptoms of psoriasis?
The main symptoms of the most common type of psoriasis - which is called plaque psoriasis - are itchy and sometimes painful dry patches and scales on the skin. This type of psoriasis affects about 90% of people with the condition and most commonly affects the scalp, back, elbows and knees. Other types of psoriasis that occur less often include nail psoriasis, guttate psoriasis, and inverse psoriasis. 1-5
What are the risk factors for having psoriasis?
Psoriasis has a strong genetic predisposition, and having a family history of the condition is an important risk factor for developing the disease. Moreover, there are many well-established triggers for the disease, including skin injuries, respiratory infections, use of certain medications, weather conditions, smoking, and alcohol consumption. 6-9
Genetic predisposition
Psoriasis has a strong genetic predisposition, with a heritability of more than 60%; additionally, more than 40 genes have been identified as playing a significant role in the disease. Worldwide, a higher incidence of psoriasis occurs within families, and having a family history of the condition is an important risk factor for developing the disease. Importantly, the development of new treatments for psoriasis has been focused on the genetic component of the disease.1-6
Skin injuries
One of the well-established triggers for psoriasis is skin injuries, including surgical incisions, cuts, bites, and tattoos. Two main reasons are identified for this association. First, the injuries lead to a release of pro-inflammatory substances that are involved in psoriasis flare-ups, and second, scratching the often itchy skin lesions caused by the disease can worsen the symptoms.7
Respiratory infections
Respiratory infections are another important trigger reported for psoriasis. Specifically, a strong association is described between streptococcal infections of the throat, mainly in children and adolescents, and initiation and exacerbation of guttate psoriasis and chronic plaque psoriasis.6
Certain medications
The use of certain medications is an acknowledged trigger to induce or aggravate psoriasis, possibly by causing changes in the immune system and in the proliferation of skin cells. The medications that have been described as triggers for the disease include lithium; non-steroidal anti-inflammatories such as ibuprofen and diclofenac; beta-blockers, such as bisoprolol and carvedilol; and angiotensin-converting enzyme inhibitors, such as enalapril and ramipril.5,6
History of skin infections
A diagnosis of psoriasis is sometimes associated with infections of the skin. Additionally, the presence of several bacteria, such as Staphylococcus Aureus, and fungi in the skin, have been implicated in the development of the disease in genetically predisposed people.8
Weather conditions
Weather conditions are another important trigger for psoriasis: sun exposure usually has beneficial effects for the condition and dry weather is prejudicial. As such, cold and dry weather can lead to psoriasis flare-ups. However, less commonly, sun exposure can also serve as a trigger for the disease, with symptoms occurring more in hot and dry weather for some people.9
Smoking and heavy alcohol consumption
Smoking and second-hand smoke serve as triggers for psoriasis, possibly by causing alterations in the immune system. The risk of developing psoriasis is not only higher in smokers compared to non-smokers, but the risk and severity are also higher with higher intensity of smoking. 1-6
A similar association is described between alcohol consumption and psoriasis, also possibly related to changes in the immune system. People who consume alcohol have a higher risk of developing the disease, and the risk and severity of the disease are higher with higher amounts of alcohol consumption. 1-6
Summary
Psoriasis is a common non-communicable skin disease that involves genetics, environmental factors, and immune system deregulation. Symptoms of the disease most often include itchy and sore dry patches and scales in the skin. The condition has a strong genetic predisposition, with a heritability higher than 60%.
There are many well-established triggers for the disease, including skin injuries, like surgical incisions, cuts, bites, and tattoos; respiratory infections, especially streptococcal throat infections; use of certain medications, such as lithium, anti-inflammatories and beta-blockers. A history of skin infection and skin microbiome, weather conditions (mainly cold and dry weather), smoking and alcohol consumption are also triggers of the disease.
References
- World Health Organization. Global Report on Psoriasis. World Health Organization; 2016.
- Griffiths CEM, Armstrong AW, Gudjonsson JE, Barker JNWN. Psoriasis. Lancet 2021;397:1301–15.
- Rendon A, Schäkel K. Psoriasis Pathogenesis and Treatment. Int J Mol Sci 2019;20:1475.
- Basko-Plluska JL, Petronic-Rosic V. Psoriasis: epidemiology, natural history, and differential diagnosis. PTT 2012;2:67–76.
- Boehncke WH, Schön MP. Psoriasis. Lancet. 2015 Sep 5;386(9997):983-94.
- Kamiya K, Kishimoto M, Sugai J, Komine M, Ohtsuki M. Risk Factors for the Development of Psoriasis. Int J Mol Sci. 2019 Sep 5;20(18):4347.
- Furue K, Ulzii D, Tanaka Y, Ito T, Tsuji G, Kido‐Nakahara M, et al. Pathogenic implication of epidermal scratch injury in psoriasis and atopic dermatitis. J Dermatol 2020;47:979–88.
- Fry L, Baker BS, Powles AV, Fahlen A, Engstrand L. Is chronic plaque psoriasis triggered by microbiota in the skin? Br J Dermatol. 2013 Jul;169(1):47-52.
- Balato N, Costanzo LD, Patruno C, Patrì A, Ayala F. Effect of weather and environmental factors on the clinical course of psoriasis. Occup Environ Med 2013;70:600–600.
