Understanding psoriasis: Types, symptoms, and who can be affected

Date of preparation: December 2024

Understanding psoriasis: Types, symptoms and who can be affected

Psoriasis is a common, chronic inflammatory condition caused by dysfunction of the immune system, which results in skin cells reproducing at a faster rate than normal.^1–3 As a consequence, raised patches form on the surface of the skin, which can appear red or purple and be flaky, itchy and scaly.² 

Several other serious health conditions have been associated with psoriasis, including diabetes, obesity, cardiovascular disease, depression, stroke and psoriatic arthritis – a chronic disease that causes inflammation, swelling and pain in the joints.^1,4

Prevalence of psoriasis 

Psoriasis affects approximately 125 million people worldwide and is a life-long condition for which there is no cure.^2,3,5 

Psoriasis occurs more frequently in adults than children. The prevalence of psoriasis in adults varies substantially depending on location.⁶ Estimates of psoriasis prevalence range from 0.14% (95% uncertainty interval 0.05–0.40%) in East Asia to 1.99% (0.64–6.60%) in Australasia (i.e., Australia, Indonesia, New Zealand and Papua New Guinea).⁷ 

Psoriasis is more common in high-income regions, including Australasia, Western Europe, Central Europe and North America, where 1.5–2% of people are estimated to be affected.⁷

Figure 1: Heatmap showing the prevalence of psoriasis in both adults and children across the world⁸

The prevalence of psoriasis is steadily increasing over time.6,9 This may be due to increased awareness of the disease among physicians and patients.⁹

Who can be affected by psoriasis?

Women and men of all ages and ethnicities can be affected by psoriasis.^10,11 

The prevalence of psoriasis increases with age until approximately 60 or 70 years.⁹ Two peaks of psoriasis onset are observed at 30–39 and 60–69 years of age, which correspond with the classification of chronic plaque psoriasis as early-onset disease (type I; ≤40 years of age) and late-onset disease (type II; >40 years of age).^9,12 

Women and men are equally affected by psoriasis, although the age at psoriasis onset may be slightly earlier in women.⁹ 

The prevalence of psoriasis varies with ethnicity; White people are more likely to develop the condition than other ethnic groups.^10,11

Symptoms of psoriasis

Symptoms of psoriasis can vary from person to person and generally include flaking, scaling, itching and scratching, rashes, skin pain, bleeding, redness, skin drying and cracking, and physical discomfort.¹¹ 

Psoriasis can flare up anywhere on the body; symptoms mostly occur on the lower back, knees, elbows, legs, soles of the feet, scalp, face and palms, but can also affect the hands, nails, skin folds and genital area^.2,3,11,13

Types of psoriasis^3,12

There are many types of psoriasis, although plaque psoriasis is the most prevalent, comprising approximately 90% of all psoriasis cases.^3,14

Plaque Psoriasis

Plaque psoriasis is characterised by well-demarcated, erythematous, scaly plaques, which can involve any part of the skin, but most commonly the extensor surfaces (such as the elbows and knees) and the scalp.

Figure 2: Plaque Psoriasis ©[fusssergei]/Adobe Stock.

Nail Psoriasis 

Nail psoriasis affects only fingernails and toenails.

Figure 3: Nail Psoriasis ©[Fabrizio]/Adobe Stock.

Guttate Psoriasis

Guttate psoriasis primarily affects young adults and children and is characterised by small, drop-shaped, scaling spots on the trunk, arms or legs.

Figure 4: Guttate Psoriasis ©[Ольга Тернавская]/Adobe Stock.

Inverse Psoriasis 

Inverse psoriasis mainly affects the skin folds of the groin, buttocks and breasts and is characterised by skin inflammation that is aggravated by friction/sweating.

Figure 5: Inverse Psoriasis ©[vvoe]/Adobe Stock.

Pustular Psoriasis

Pustular psoriasis is a rare form of psoriasis characterised by pus-filled blisters, which involves either small area such as palms of the hands, fingertips, nails and soles of the feet, or the entire body surface.

Figure 6: Pustular Psoriasis

Erythrodermic Psoriasis

Erythrodermic psoriasis is the rarest form of psoriasis and is characterised by a peeling rash that can cover the entire body.

Figure 7: Erythrodermic Psoriasis ©[Nikkikii]/Adobe Stock.

Severity of psoriasis

The severity of psoriasis is typically classified as mild, moderate or severe. While there is currently no consensus on how this is defined, psoriasis is typically considered severe if it:¹⁷ 

• Affects over 10% of the body surface area (see figure 8). 
• Affects areas of the body where symptoms have a greater impact on the patient (e.g., the scalp, hands, feet, groin, or between the skin folds). 
• Significantly impacts quality of life. 

Light therapy or systemic medications are typically required to control moderate-to-severe psoriasis disease.¹⁸

Figure 8: Moderate-to-severe psoriasis affects more than 3% of skin¹⁷

Nearly half of the patients with psoriasis have a moderate-to-severe form of the disease.¹⁴ This has a substantial impact on quality of life, with over half of the patients with moderate (56%) or severe (66%) psoriasis reporting their psoriasis had a very large to extremely large effect on their quality of life in a global survey.19 Only 7% of patients with moderate disease, and 5% of patients with severe disease, said their psoriasis had no effect on their life.¹⁷ 

The severity of psoriasis has been linked to alcohol consumption, obesity and stress.^1,18,19 Patients may resort to negative coping strategies, such as comfort eating, drinking alcohol and social isolation, which negatively impact psoriasis treatment outcomes or increase disease severity.^17,20–24 This potentially perpetuates a cycle of poor disease control and negative coping strategies that leads to psoriasis worsening.

Severe psoriasis is associated with increased risk of comorbidities

The risk of cardiovascular diseases (e.g., myocardial infarction, atherosclerosis and heart failure) and diabetes mellitus is higher in patients with more severe forms of psoriasis.^15,25 

Severe psoriasis is also associated with greater risk of depression and anxiety, as well as increased likelihood of suicide ideation or intent.^20,26