Introduction

Psoriasis is a long-lasting skin disorder that affects tens of millions of people worldwide.¹ This chronic skin condition occurs when the immune system causes skin cells grow much too quickly, resulting in thick, red patches that can also become scaly.² There are a number of psoriasis types, but the two that are most often confused are plaque psoriasis and pustular psoriasis.

Plaque psoriasis is the most common and represents 80-90% of psoriasis.^2,3 The plaque appears  as raised, red patches covered with silvery-white scales.³ Pustular psoriasis is less common but can be more serious.⁴ Pustular psoriasis presents with white pustules (bumps filled with non-infectious pus) on swollen skin.⁴

It is important to know the differences between these two types of psoriasis. They may look similar at first glance, but they behave differently, are triggered by different factors, and often require very different treatments. Being aware of the differences is a good way for clinicians to help their patients obtain an accurate diagnosis and treatment.

What is plaque psoriasis?

It is the most common type of psoriasis.³ It appears as raised red spots on the skin with silvery-white scales.³ These spots, commonly referred to as plaques, can be different sizes and might join together to cover larger areas of skin.

The plaques are most often found on elbows, knees, scalp, and lower back, but can develop anywhere on the body.³ The skin in those areas may feel itchy, sore, or tight, and scratching one area may intensify the itch.

Plaque psoriasis is recognised as a chronic condition, as it usually comes and goes over a person's lifetime.³ Many people experience flare-ups, where the skin appears worse, and at some points feel better.³

While plaque psoriasis is not contagious, it can still have a negative effect on people's confidence and quality of life. Many people feel self-conscious about their skin and feel heightened uncertainty regarding their psoriatic condition, especially during flare-ups. However, many people can control their flare-ups and manage their symptoms with appropriate treatment.

What is pustular psoriasis?

Pustular psoriasis is much less common than plaque psoriasis. Plaque psoriasis causes drg, scaly patches to form on the skin, while pustular psoriasis leads to red, inflamed areas covered with white or yellowish pustules - small, non-infectious bumps filled with pus.⁴ Again, the pustules do not come from an infection, but are due to the skin being in an overactive state through the immune process.

There are two types of pustular psoriasis:⁴

• Localised pustular psoriasis is generally in one or more specific locations, small patches or areas, presenting on areas of skin like the palms of the hands or soles of the feet⁵
• Generalised pustular psoriasis (or von zumbusch psoriasis) is less common, but more widespread and severe.^4,6 This condition affects a larger areas of the body and the pustules present systemically, with fever, chills, tiredness, and/or other symptoms⁶

Pustular psoriasis can be a rapidly presenting disorder and may flare quickly. In an infant, this is concerning for parents but will likely resolve on its own over the weeks and will usually not be important. In a neonate, it can reach the point of requiring hospitalisation based on its severity.

For early diagnosis, it is very important that a proper diagnosis is made because pustular psoriasis looks very different from plaque psoriasis, and can be much more severe.

Key differences at a glance

Plaque psoriasis and pustular psoriasis are both types of psoriasis, but they differ in terms of surface appearances, all body sensation, and impact on a person's daily activities.

Visual appearance

• Plaque psoriasis appears red, raised, and covered with silvery plaques on the skin³
• Pustular psoriasis appears as white pustules (bumps filled with pus) on red skin⁵

Pain and discomfort

• Plaque psoriasis is often characterised as itchy, painful, and uncomfortable³
• Pustular psoriasis pustules can be painful and may be accompanied by a burning or itchy sensation⁵

Severity of psoriasis

• Plaque psoriasis is generally chronic and relapsing, but becomes life threatening
• Pustular psoriasis may present suddenly, and when generalised, may be acute and severe enough to require medical assistance

Age of onset

• Plaque psoriasis may present at any age, most often during adolescence or adulthood
• Pustular psoriasis may have sudden presentations in adults or gradually arise in newborns

Systemic involvement

• Plaque psoriasis mainly affects the skin, while psoriatic arthritis is a related condition that primarily involves the joints³
• Pustular psoriasis can involve the entire body and may be accompanied by fever, fatigue, and/or other serious systemic symptoms⁵

These differences matter (even if only slightly) - to help the doctor with their treatment plan and their family with understanding the nature of the disease.

Triggers 

Both plaque and pustular psoriasis can be flared due to certain factors, However, different triggers tend to affect specific forms of the condition. Understanding the triggers may help patients get better control of their disease.

Common triggers 

Stress, infections, smoking, alcohol, and some medications, like beta-blockers or lithium, will cause either type of psoriasis to flare.  

Plaque psoriasis triggers 

• More familial and genetic aspects
• Colder weather, dry skin, or even mild trauma (known as the "Koebner phenomenon," whereby plaques develop over scratched or injured skin) may instigate flare-ups
• Conditions associated with obesity, diabetes, or heart disease may flare up as well

Pustular psoriasis triggers 

• Pustular is brought on by the abrupt stopping of steroid drugs (probably the commonest trigger of generalised pustular psoriasis)⁵
• Can also worsen due to pregnancy, certain infections, or abrupt medication withdrawal⁷
• Develops unexpectedly and spreads in a few hours 

Pustular psoriasis, by virtue of being very swift in progression, will have triggers that must be identified and avoided.

Treatment strategies 

Plaque psoriasis

Treatments are topical therapies, i.e. creams or ointments- corticosteroids, Vitamin D analogues (the most common is calcipotriene), or coal tar products, are the first treatment options for mild disease.⁸

• Phototherapy: UV light exposure in a controlled office setting can accelerate the healing of psoriasis plaques
• Systemic therapy: Systemic medicines such as methotrexate, cyclosporine, or acitretin may be used for moderate to severe plaque psoriasis
• Biologics: Newer medications such as TNF inhibitors, IL-17 inhibitors, or IL-23 inhibitors, these often effectively target certain aspects of the immune system⁹ 

Pustular psoriasis

Urgent medical treatment: Generalised pustular psoriasis may need treatment under hospitilisation, especially if fever and dehydration are present.

• Systemic therapies: These systemic medicines, such as acitretin, methotrexate, or cyclosporine, are often used to help control flare-ups
• Biologics: Some biologics have been recently either approved or studied for pustular psoriasis. For example, IL-36 inhibitors may specifically inhibit signalling pathways leading to pustules^9,10
• Supportive care: Closely related to the care of the patients are the pain control, hydration, and infection prevention, especially in the cases of severe pustular psoriasis

These therapies allow plaque psoriasis to be chronically treated in an outpatient setting. Otherwise, more aggressive therapy may be indicated for pustular psoriasis.

FAQs

Is pustular psoriasis worse than plaque psoriasis? 

Yes. While plaque psoriasis usually becomes chronic and stable, generalosed pustular psoriasis, if untreated, may lead to fever, infections, and complications. 

Can you have plaque psoriasis and pustular psoriasis at the same time? 

Yes. A patient with longstanding plaque psoriasis may flare with pustular psoriasis, particularly with changing medications. 

Are these conditions contagious? 

No. Plague psoriasis and pustular psoriasis are not contagious. These are immune-mediated diseases, again, immune-mediated, not infectious in nature. 

Can lifestyle changes help? 

Yes. Not only can you avoid known triggers, and reduce stress, but you can also lose weight and reduce smoking risks, which contributes to further reducing flares and improves treatment outcome.

Summary

Though both plaque psoriasis and pustular psoriasis are immune-mediated atypical skin reactions, there are some very key differences. Plaque psoriasis represents the most common form of psoriasis, characterised by red, scaly patches that rise and fall over time; pustular psoriasis is less common and characterised by white blister-like pustules over very red and inflamed skin and can have an acute start and serious clinical symptomatology. The triggers for the clinical response are similar in both forms of psoriasis, as stress, infection and medications can trigger a flare in both forms. 

However, pustular psoriasis, in particular, has an added association with infections, fungal and/or otherwise, with systemic anti-infective treatment, withdrawal of steroids, together with intrauterine device-related, as well as medication changes. Treatment approaches are also very different and can differ greatly depending on what the patient has, as plaque psoriasis can lead to topical creams, light therapy, or biologics or whatever treatment works for the patient, whereas pustular psoriasis can lead to a hospitalisation or much stronger medications. 

It is helpful for an individual with pustular psoriasis, as well as plaque psoriasis, to understand the differences. With an accurate diagnosis and ongoing care with your provider and healthcare team, the vast majority of either type of psoriasis will be able to control their flares and live their best life!