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Understanding Pustular Psoriasis

This rare type of psoriasis can be difficult to treat and live with, but dermatologists may soon have more effective, targeted therapies.

Karl Smith woke up one morning in 2015 and noticed reddened skin over his right heel and toes. The next day, pus-filled bumps started to crop up inside the red patches. They caused intense pain and made walking and driving difficult.

Smith, now 60, immediately made an appointment with the dermatologist who treated him for the plaque psoriasis he has had since his teens. Looking at the pus spots, called pustules, his dermatologist quickly made a new diagnosis: palmoplantar pustulosis, an often painful type of pustular psoriasis.

Smith, who lives in Wilmington, Delaware, also has guttate psoriasis and psoriatic arthritis (PsA). But he knew little about this pustular form of psoriasis. “It arrived so quickly and really took me by surprise,” he says. “The pain drove me nuts, and it took away my driving foot at a time when I was looking for a job and needed to go to interviews. It was a very trying time for me with psoriasis – my worst experience in all my years with the disease.”

A sudden, unpredictable flare is one of the hallmarks of pustular psoriasis, says Melinda Gooderham, M.D., a board-certified dermatologist and medical director at the SKiN Centre for Dermatology in Peterborough, Ontario, Canada, and assistant professor of medicine at Queen’s University in Kingston. “The unpredictability is one of the main ways pustular psoriasis differs from plaque psoriasis, which tends to be a very stable disease,” she says. “Because of that unpredictability, pustular psoriasis often causes more anxiety than other types of psoriasis.”

Smith was hit hard by the experience.

“The pain was constant and made it hard to sleep. The outbreak looked bad, and kids would ask me about it,” he says. He also felt isolated. Psoriasis runs in his family, but none of his relatives knew much about pustular psoriasis or could relate to what he was going through.

The relative rarity of pustular psoriasis means that not all primary care physicians or even all dermatologists are well-versed in diagnosing and treating the disease. The dermatologist Smith saw, for example, consulted a colleague who had more experience with pustular forms of psoriasis.

What Causes the Pustules?

The first thing to understand, says Dr. Gooderham, is that the pustules of pustular psoriasis do not mean you have an infection. “It looks like an infection, and that is probably the first assumption people make when they see the pustules,” she says. “But despite its appearance, it’s not an infection, and it’s not contagious. Like other forms of psoriasis, it’s caused by inflammation in the body.”

The pus in the bumps is made up of neutrophils, a type of cell that normally fights infection. “That’s why we see pus when we have an infection, but neutrophils can also be called to the skin for different reasons,” she says. “With pustular psoriasis, the immune system is making a kind of ‘false call’ for them to come to the skin.”

Pustular Psoriasis: Triggers and Types

There are several types of pustular psoriasis. All are rare, and all feature patches of reddened or discolored skin dotted with pus-filled bumps. It is important to note that psoriasis may look different on different skin types. On lighter skin types, psoriasis often looks red with a silvery scale on top. [1] On darker skin types, psoriasis may look salmon, dark brown, purple, or violet with gray scale. [1] [2]

Flares tend to occur in a cycle of symptoms:

  1. Patches appear suddenly and quickly develop pustules.
  2. Then, the pustules can join together and burst, which can leave skin tender, raw, and scaly.
  3. New pustules can form on the tender skin and restart the cycle.

Some people with pustular psoriasis already have another type of psoriasis. “Patients who have stable plaque psoriasis can have their immune systems triggered by something that causes pustular flares,” says Dr. Gooderham. “But you can have no personal or family history of psoriasis and still develop one of the pustular forms of the disease.”

One trigger is the withdrawal of a treatment that modulates or suppresses the immune system. “If you suddenly stop one of these drugs, a steroid or cyclosporine, for example, your immune system can rebound with a pustular flare,” she says.

Other triggers include: [3]

  • Infections
  • Overexposure to sunlight or another type of ultraviolet light
  • Emotional stress
  • Pregnancy

Different types of pustular psoriasis affect different parts of the body. People usually have one type versus multiple forms of the disease, Dr. Gooderham says. “There is still a controversy over whether these different types are all on the same spectrum [of disease] or whether they are unique conditions that we’re just categorizing together because they all feature pustules,” she says.

Generalized pustular psoriasis (GPP): When this severe form of pustular psoriasis flares, pustules often cover large areas of the body. It can cause fever, shivers, intense itching, a rapid pulse, fatigue, headache, nausea, muscle weakness, and joint pain.

“People often feel very sick when they have a GPP flare,” Dr. Gooderham says. Flares can also cause life-threatening complications. Blood pressure can drop suddenly, for example. That is why dermatologists sometimes admit patients with GPP flares to the hospital, where they can be watched and treated quickly for the condition and any complications. [4]

People with GPP tend to have sudden attacks that last for a few weeks, followed by periods in which their skin partly or completely clears up. [4]

Some women have a flare of GPP when they are pregnant, usually in their third trimester. [4] This type of GPP is called pustular psoriasis of pregnancy or impetigo herpetiformis. “With treatment, these flares usually clear up when women are no longer pregnant. It doesn’t usually come back unless they have another pregnancy,” Dr. Gooderham says. “If you’ve had a flare during pregnancy, and you get pregnant again, your doctor should watch closely for another flare.”

GPP usually affects adults, but children can develop it too. Often, these children have genetic changes, or mutations, linked to a higher risk of GPP, Dr. Gooderham says. The most common mutations linked to GPP occur in the IL36RN gene. It controls a protein called interleukin (IL)-36. When the signals of the gene are abnormal, this protein gets out of control and causes inflammation in the skin. [5] “When people have that genetic predisposition, they tend to have GPP at younger ages, which means it can sometimes come out in childhood,” she says.  

Palmoplantar pustulosis (PPP): Karl Smith was diagnosed with this type of pustular psoriasis, which affects the palms, the soles of the feet, or both. It tends to affect fleshy areas, such as the base of the thumb or the side of the heel. It’s more common in women and in people who smoke. [5]

When PPP flares, it causes discolored skin with large yellow pustules scattered throughout. The pustules can darken and turn brown as they dry. Affected skin can scale, crack, and fissure, and outbreaks can last for a considerable amount of time. It took Smith a year to get control of the flare that started on his toes and heel and gradually crept up the back of his lower leg.

PPP is a type of psoriasis that can be particularly hard for people to cope with. This was true for Smith, who had to use crutches for a time and felt more depressed about his skin than at any time in his decades of living with psoriasis. “When psoriasis affects your hands or feet, it can be very visible, sometimes disabling, and have a significant negative impact on your quality of your life,” Dr. Gooderham says.

Acrodermatitis continua of Hallopeau (ACH): This type of pustular psoriasis causes pustules on the tips of the fingers or toes and sometimes under the nail. It usually starts on one finger or toe but can spread. [4]

ACH can cause bone damage and, like PPP, can be painful and disabling. “People often lose their nail or parts of their nail,” Dr. Gooderham says.

Developing a Diagnosis

Health care providers who are not familiar with pustular psoriasis can misdiagnose any type as an infection. This happens less often with ACH and PPP, which are easier to identify because not many conditions affect the hands and feet in a similar way.

The widespread pustules of GPP, however, can look like several other conditions. “For example, acute generalized exanthematous pustulosis, which is usually caused by a reaction to an antibiotic, looks almost identical,” Dr. Gooderham says. “That means we may need other clues to help us narrow down a diagnosis.”

To make a diagnosis of pustular psoriasis, a dermatologist will do a physical exam and take a complete medical history. He or she may also test a sample of pus or affected skin to make sure the outbreak is not caused by an infection and do blood tests to rule out other conditions.  

Treatment Options

When pustular psoriasis is confined to the hands or feet, as with PPP and ACH, dermatologists may start treatment with a topical medication, Dr. Gooderham says. “If topicals don’t improve symptoms, or [symptoms] are severe, we may use traditional immune-suppressing [or immune-modulating] medications, such as methotrexate, or biologics,” she adds. 

Treatment for GPP usually starts with a biologic or an oral medication and may also include the use of topicals, says Dr. Gooderham, who acknowledges that finding a treatment plan that works can take time. “Right now, we have many drugs we can try, but there’s no specific targeted therapy for pustular psoriasis. What works for one person may [cause a] flare [for] another,” she says. “That means people may need to try several medications before they find the one that improves their symptoms.”

Topicals did not help Karl Smith with PPP, but his outbreak started to resolve after four months of treatment with a biologic. Keeping the affected area well-moisturized with petroleum jelly and organic aloe vera and covering it at night with plastic wrap eased his pain. Although he did not enjoy using crutches, taking pressure off his affected foot helped. He also worked on managing his stress and taking care of himself. “I sometimes dealt with it by overeating and hiding away,” he says. “But you can’t do that – or lambaste yourself – and get better.”

After a year of biologic therapy and diligent self-care, the pustules and pain Smith experienced are gone, although the skin on his toes remains red. “Since then, it has not come back, but it’s always on my mind,” he says. “Now I want to use my lifelong experience as a person with psoriasis to help educate others with the condition.”

In addition to getting regular care from a dermatologist, Dr. Gooderham advises a healthy lifestyle, regular moisturization, and, if you smoke, quitting. “It’s also important to get help if you’re struggling with depression or anxiety,” she says. “Talk to your doctor. There are things that can help, whether it’s more support, therapy, or medications.”

She adds that there may soon be better treatments for pustular psoriasis. Researchers are testing two new biologics that target IL-36, the protein that is a key cause of inflammation in GPP. Clinical trials are in early stages, but so far, the treatments show the potential to be safe and effective. [6]

“Pustular psoriasis is being studied more now than it ever has been before, and advances in understanding are leading us to new, more targeted treatments,” says Dr. Gooderham. “I think within the next five to 10 years we’re going to know a lot more about it and have much better treatments available to manage it.”

If you would like to learn more about pustular psoriasis, or if you want to explore your treatment options for whatever type of psoriasis you experience, the National Psoriasis Foundation Patient Navigation Center is ready to help.

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References

1.      Kaufman BP, Alexis AF. Psoriasis in skin of color: Insights into the epidemiology, clinical presentation, genetics, quality-of-life impact, and treatment of psoriasis in non-white racial/ethnic groups [published correction appears in Am J Clin Dermatol. Feb 16, 2018]. Am J Clin Dermatol. 2018; 19(3): 405-423. doi:10.1007/s40257-017-0332-7.

2.      American Academy of Dermatology. Can you get psoriasis if you have skin of color? aad.org/public/diseases/psoriasis/treatment/could-have/skin-color.

3.      National Psoriasis Foundation. Pustular psoriasis. Updated Jun 2021. psoriasis.org/pustular/.

4.      Bachelez H. Pustular psoriasis: The dawn of a new era. Acta Derm Venereol. Jan 30, 2020; 100(3): adv00034. doi:10.2340/00015555-3388.

5.      Twelves S, Mostafa A, Dand N, Burri E. Clinical and genetic differences between pustular psoriasis subtypes. J Allergy Clin Immunol. Mar 2019; 143(3): 1021-1026. doi:10.1016/j.jaci.2018.06.038.

6.      Jesitus J. IL-36 inhibitors on the horizon for generalized pustular psoriasis. Dermatology Times. May 2021. dermatologytimes.com/view/il-36-inhibitors-on-the-horizon-for-generalized-pustular-psoriasis.

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