An Overview of Pustular Psoriasis

Pustular psoriasis is a rare type of psoriasis that causes tender, pus-filled blisters called pustules. The pustules are red and scaly and in some cases may cover a large part of the body. People who have widespread pustules need to seek immediate medical attention, as the condition can be life-threatening.

While accounting for only .6% to 2.4% of psoriasis cases, pustular psoriasis is arguably more serious than most other forms of the disease.

This article looks at pustular psoriasis and its symptoms, causes, diagnosis, and treatment. It also discusses ways you might be able to prevent this dangerous form of psoriasis.

Symptoms of Pustular Psoriasis

Pustular psoriasis differs from the "classic" form of the disease, known as plaque psoriasis. In plaque psoriasis, dry, red lesions covered with silvery-white scales develop on the skin. With pustular psoriasis, the lesions form pus-filled blisters called pustules.

There are three major types of pustular psoriasis. Each of these types differ in location, severity, and medical response.

Pustular psoriasis looks different depending on which type you have. Generally speaking, the pustules appear as small white blisters similar to pimples but without the inflamed borders. They are usually closely clustered and set atop a patch of red, inflamed skin.

The pustules easily erupt and can be extremely itchy and painful. After breaking open, the pustules form crusty, peeling lesions that heal slowly.

The three primary types of pustular psoriasis are:

• Palmoplantar pustulosis (PPP) is the type that develops on small areas of the body, typically the palms of the hands or soles of the feet. PPP can be recurrent and is most common in people who smoke.
• Acrodermatitis continua of Hallopeau (ACH) is characterized by small but extremely painful pustules that appear on the fingertips or toes and occasionally spread to the hands or soles. Nail and joint damage have been known to occur. The pain is often extreme enough to make walking or grasping objects difficult.
• Von Zumbusch psoriasis, also known as generalized pustular psoriasis, is characterized by widespread itchy pustules. Other symptoms include fatigue, fever, chills, nausea, headache, muscle weakness, joint pain, and weight loss. The extreme peeling of skin can lead to rapid dehydration, tachycardia (rapid heart rate), and an increased risk of infection. If not properly treated, Von Zumbusch psoriasis can become life-threatening.

What Causes Pustular Psoriasis?

All psoriatic diseases are characterized by an abnormal autoimmune response in which the immune system suddenly and inexplicably attacks normal skin cells. The ensuing inflammation prompts the cells to multiply at an accelerated rate. This causes them to build one on top of the other faster than they can be shed.

The cause of pustular psoriasis is poorly understood. It is believed to be linked to a sudden, extreme burst of inflammation in the transition between the upper layer of skin (epidermis) and the layer just below (dermis). In addition to triggering plaque, the inflammation causes the rapid death of defensive white blood cells. This, paired with the accumulation of lymph fluid, is what causes pus to form.

Pustular psoriasis is associated with specific triggers that can give rise to acute episodes known as flares. In many cases, a person with plaque psoriasis will suddenly develop pustular psoriasis in response to these triggers. Pustular psoriasis triggers may include:

• Drug reactions: This is the most common cause and can involve a wide range of medications.
• Strong topical medications, in particular, can trigger pustular psoriasis, including psoriasis remedies like crude coal tar, anthralin, steroids under occlusion, and zinc pyrithione in shampoo.
• Abrupt discontinuation of prednisone: This can trigger a severe rebound of psoriasis symptoms unless the prednisone dose is gradually tapered.
• Skin infections (e.g., staphylococcal and streptococcal)
• Phototherapy: On rare occasions, this psoriasis treatment can trigger a severe flare. In addition to phototherapy, excessive sun exposure can act as a trigger.
• Pregnancy has been known to incite a pustular outbreak, most often during the third trimester. This can lead to miscarriage or stillbirth.

Diagnosis

The diagnosis of pustular psoriasis starts with a physical exam and a review of your medical history. Because pustular psoriasis often occurs in people with a history of plaque psoriasis, these evaluations may be all that is needed to render a diagnosis.

In the end, there are no lab or imaging tests that can definitively diagnose psoriasis of any type. The diagnosis is based largely on symptoms, individual risk factors, a review of potential triggers, and clinician experience.

With that being said, your healthcare provider will make every effort to ascertain whether there are other explanations for the symptoms. This is referred to as the differential diagnosis.

One of the ways to do this is to send a pus sample to a pathologist for evaluation. Since pustular psoriasis is not caused by an infection, there should be no evidence of a bacteria, virus, or fungus unless the infection was secondary—one that occurred as the result of the skin rupture.

Some of the conditions that can be mistaken for pustular psoriasis include:

• Acute generalized exanthematous pustulosis
• Drug eruption reaction
• Pemphigus vulgaris
• Pemphigus foliaceous
• Impetigo
• Dermatitis Herpetiformis
• Infected eczema
• Erythroderma
• Acute cutaneous lupus
• Dyshidrotic eczema
• Disseminated herpes simplex virus

Treatment

The treatment of pustular psoriasis also varies by disease type. Both PPP and ACH are usually treated at home, while Von Zumbusch psoriasis almost always requires hospitalization.

Palmoplantar Pustular Psoriasis

Mild cases may only require topical treatments, such as hydrocortisone, coal tar, or salicylic acid creams or lotions. These may be applied in occlusion, meaning the skin is covered (say, with a sock or glove) so that the medication can be more readily absorbed.

Moderate to severe cases may require oral medications such as:

• Soriatane (acitretin), a retinoid drug that tempers the hyperproduction of skin cells
• Disease-modifying antirheumatic drugs (DMARDs) like methotrexate or cyclosporine, which temper the overall immune response

Another option is psoralen ultraviolet light A (PUVA), a form of phototherapy in which a psoralen drug sensitizes the skin to UV light. This may be used if the pustules are less responsive to treatment.

Acrodermatitis Continua

The treatment approach for ACH is similar to that of PPP, although, for reasons not entirely understood, people with ACH tend to be less responsive to such treatments.

To bolster the effectiveness of ACH treatment, injectable biological drugs like Humira (adalimumab) and Enbrel (etanercept) are often combined with oral methotrexate.

Von Zumbusch Psoriasis

Most cases of Von Zumbusch psoriasis require hospitalization with intravenous (IV) fluids to prevent dehydration and IV antibiotics to prevent infections.

Generalized pustular psoriasis is treated by covering the skin in dressings soaked in a mixture of aluminum acetate and water (Burow's solution). The preparation has astringent and antibacterial properties that can reduce swelling and aid with healing.

Prevention

Pustular psoriasis can be extremely distressing both physically and emotionally. There is little you can do to avoid getting pustular psoriasis since the causes are so varied and multidimensional. But, there are things you can do to reduce your risk:

• Stop smoking: Smoking is one of the main risk factors for PPP, but it also contributes to ACH and Von Zumbusch. If you cannot stop on your own, ask your healthcare provider about smoking cessation tools.
• Lose weight: The increased accumulation of fat translates to increased levels of systemic inflammation. By eating right and exercising regularly, you can reduce the inflammatory burden on your body and, with it, the risk of flares.
• Avoid excessive sun exposure: Limited sun exposure can reduce the hyperproduction of skin cells. But, overexposure can have the opposite effect and trigger an acute flare. Limit your daily exposure to 15 to 20 minutes, and wear plenty of sunscreen.
• Manage your stress: Mind-body therapies like meditation, guided imagery, and progressive muscle relaxation (PMR) have their place in managing psoriasis symptoms and reducing the risk of flares.
• Cut back on alcohol: Like smoking, drinking excessively can increase your risk of flares. This is particularly true with non-light beer. If you cannot cut back entirely, limit yourself to no more than two to three drinks daily, replacing non-light beer with light beer or wine.

Summary

Pustular psoriasis is a rare type of psoriasis that causes pus-filled blisters to form on affected patches of skin. In some types, these blisters may appear over large parts of the body. When this happens, you should seek immediate medical attention.

Like other types of psoriasis, pustular psoriasis can be triggered by things like medications and skin infections. Mild cases are usually treated with topical medication; serious cases may require hospitalization, antibiotics, and IV fluids.

You may be able to reduce your risk of having a pustular psoriasis flare by making lifestyle changes including quitting smoking, losing weight, and managing your stress.