Pustular Psoriasis

Pustular psoriasis is a rare and serious form of psoriasis that causes painful, pus-filled blisters to appear on inflamed skin. While it affects only about 3% of people with psoriasis, this condition requires prompt medical attention, especially when it spreads quickly across large areas of the body.

Table of contents

• What is pustular psoriasis?
• Symptoms
• Types of pustular psoriasis
• Causes and triggers
• Diagnosis
• Treatment and management
• Outlook and prognosis

What is pustular psoriasis?

Pustular psoriasis is a rare type of psoriasis, which is a chronic disease caused by an overactive immune system that speeds up skin cell growth^[1]. This condition is considered a variant of psoriasis vulgaris and affects about 3% of people living with psoriasis^[1].

The disease is characterized by yellowish or white bumps filled with pus, called pustules, which appear on an inflamed or reddened base^[3]. These pustules contain a sterile fluid caused by inflammation, not bacteria, which means the condition is not contagious and cannot be spread from person to person^[1].

Pustular psoriasis may be more common in some skin of color ethnicities^[1]. The condition affects both children and adults, with a bimodal age distribution. In adults, it most commonly appears between ages 40 to 50^[3]. Females are generally more likely to be affected, although in children between ages 3 and 16, males may be more commonly affected^[6].

Symptoms

The main symptoms of pustular psoriasis include sterile pustules, which are white or yellow, pus-filled, painful bumps that may be surrounded by inflamed or discolored skin^[1]. The condition typically presents with patches of thick, discolored, flaky and scaly skin known as plaques, which are covered with fluid-filled blisters or pustules^[2].

Common symptoms include mild to severe pain, itchiness, and tenderness of the affected skin^[2]. The pustules on the skin can join together with other fluid-filled bumps and burst open, making the skin feel very tender and sore. When pustules break open, new ones can form in the same location^[2].

Unlike chronic plaque psoriasis, which is the most common variant of psoriasis, lesions of pustular psoriasis are often tender to palpation, or touch^[3]. The pustules can turn brown, peel off, or crust over, and in some cases the skin can crack^[4].

When pustular psoriasis spreads over large areas of the body, it can cause additional symptoms such as fever, chills, severe itching, rapid heart rate, fatigue, muscle weakness, headache, joint pain, nausea, dehydration, and weight loss^[4][5].

Types of pustular psoriasis

Pustular psoriasis can be divided into two broad categories based on how and where it affects the body: generalized pustular psoriasis and localized pustular psoriasis^[2].

Generalized pustular psoriasis (GPP)

Generalized pustular psoriasis, also known as von Zumbusch psoriasis, is the rarest form of psoriasis^[2]. It affects large areas of the body and can develop suddenly and progress quickly^[1]. This severe form is characterized by recurrent flares of widespread sterile pustules with painful skin^[6].

GPP often comes with serious symptoms including fever, chills, severe itching, rapid heart rate, fatigue, and muscle weakness^[1]. The skin initially becomes fiery red and tender, and within hours, clusters of small pustules may appear in a diffuse pattern^[5]. This type can be associated with systemic inflammation affecting the liver, digestive system, muscles and joints, kidneys, or lungs^[6].

If you think you have generalized pustular psoriasis, you should see a healthcare provider immediately, as this condition can be life-threatening^[1][8].

Localized pustular psoriasis

Localized pustular psoriasis targets specific parts of the body and includes several subtypes^[2]:

Palmoplantar pustular psoriasis (PPPP), also known as palmoplantar pustulosis, affects the palms of the hands and the soles of the feet^[1]. This type often affects the base of the thumbs and the sides of the heels^[1]. The pus-filled spots can turn brown, peel off, or crust over, and the skin can crack. This form may come and go, and is more likely to occur in people who smoke^[4].

Acrodermatitis continua of Hallopeau (ACH) affects only the tips of the fingers and toes, particularly around the nails^[1]. This very rare type may appear after an injury to the skin or infection^[1]. The small, very painful lesions can make it difficult to use fingers or toes, and in rare cases can cause nail or even bone damage^[4].

Other subtypes include annular or circinate pustular psoriasis, which has a ring shape with pustules at the margins, and impetigo herpetiformis, which occurs during pregnancy and is associated with low calcium levels or infection^[4][6].

Causes and triggers

The exact cause of psoriasis is not fully understood. Pustular psoriasis occurs in genetically susceptible individuals when the overactive immune system speeds up skin cell growth^[3]. Normal skin cells completely grow and shed in about one month, but with psoriasis, skin cells do this in only three or four days. Instead of shedding, the skin cells pile up on the surface of the skin^[1].

The condition is associated with a combination of genetic and environmental risk factors. Several genetic mutations are associated with pustular psoriasis, including mutations in genes involved in regulating immune and inflammatory pathways, particularly the IL36RN gene (interleukin 36 receptor antagonist)^[6]. Patients with pustular psoriasis have an increased frequency of the HLA-B27 allele compared to the general population^[3].

Several factors may trigger pustular psoriasis. Most cases are idiopathic, meaning the cause is unknown, but identified triggers include^[1][3][6]:

• Certain medicines, including antimicrobials, systemic steroids, lithium, iodine, and some blood pressure medications
• Suddenly starting or stopping medications, particularly the abrupt withdrawal of systemic corticosteroids or ciclosporin
• Exposure to too much ultraviolet (UV) light from sunlight or sunburns
• Infections, including Streptococcus, Staphylococcus, and various viral infections
• Pregnancy
• Stress
• Low calcium levels in the blood (hypocalcemia)
• Vaccinations
• Menstruation

Inflammation caused by psoriasis can impact other organs and tissues in the body. People with psoriasis may experience related health conditions. One in three people with psoriasis may also develop psoriatic arthritis^[1].

Diagnosis

A healthcare provider will take several factors into consideration when making a diagnosis for pustular psoriasis, including the appearance and location of the pustules^[1]. The provider will ask questions about your health and examine your skin, scalp, and nails^[5].

In some cases, the provider might take a small sample of skin, called a biopsy, for examination under a microscope. This helps determine the type of psoriasis and rule out other disorders^[5].

Laboratory findings in patients with generalized pustular psoriasis may include^[5]:

• Complete blood cell count showing decreased lymphocytes and increased white blood cells, sometimes as high as 40,000 per microliter
• Elevated erythrocyte sedimentation rate (ESR)
• Elevated C-reactive protein (CRP)
• Changes in serum chemistry, including increased plasma globulins, and decreased albumin, calcium, and zinc
• Elevated liver enzymes if liver damage has occurred

Bacterial cultures of pustules are typically negative in the absence of secondary infection, as the pustules are sterile^[5].

Under the microscope, the tissue shows characteristics similar to psoriasis vulgaris, with specific features including neutrophils migrating to the epidermis and forming pustules known as spongiform pustules of Kogoj, which are characteristic of this condition^[5].

Treatment and management

Although there is no cure for pustular psoriasis, there are more effective treatments today than ever before^[1]. Treating psoriasis can help improve symptoms and may lower the risk of developing related health conditions such as psoriatic arthritis, heart disease, obesity, diabetes, and depression^[1].

There is no standard therapy for pustular psoriasis, and disease severity and extent of skin involvement help guide treatment decisions^[5]. Treatment approaches include^[1]:

Topical treatments

Topical treatments include over-the-counter products, topical steroids, and topical non-steroids. These are often used for more localized disease on the palms and soles^[12]. Topical corticosteroids are frequently prescribed medications for treating mild to moderate psoriasis and are available as oils, ointments, creams, lotions, gels, foams, sprays, and shampoos^[1].

Phototherapy

Phototherapy uses controlled exposure to light to treat psoriasis symptoms^[1].

Systemic treatments

Current recommendations for pustular psoriasis include systemic medications together with proper supportive measures. First-line therapies considered by medical boards include oral retinoids (acitretin, isotretinoin), methotrexate, cyclosporine, and infliximab^[12].

For generalized pustular psoriasis specifically, spesolimab became the first approved therapy for GPP flares in September 2022. This medication is an interleukin-36 receptor antagonist. In clinical trials, 54% of patients treated with spesolimab achieved complete clearance of pustules within one week, compared with only 6% in the placebo group^[12].

Second-line therapies include biologic agents such as etanercept, adalimumab, ustekinumab, and secukinumab^[12]. In children, acitretin, cyclosporine, methotrexate, and etanercept are options for first-line therapy, though no randomized controlled trials exist to confirm efficacy in pediatric patients^[12].

Combination therapy using both first-line and second-line agents can also be considered^[12].

Outlook and prognosis

Psoriatic disease is lifelong, and symptoms may resolve and recur throughout a person’s lifetime^[1]. Psoriasis is a chronic condition that can come and go throughout your life^[2].

While there is no cure for psoriasis, treatments today are more effective than ever before, and research into new treatments as well as a cure is ongoing^[1]. Treating psoriasis can help improve symptoms and may decrease the associated inflammation that can lead to related health conditions such as psoriatic arthritis, heart disease, and depression^[1].

There is no known way to prevent the onset of psoriasis. However, there are many ways that you can manage your triggers to reduce flares^[1]. Understanding your condition and working closely with healthcare providers can help you better manage the uncertainty that comes with living with pustular psoriasis.