Pustular Psoriasis Overview of Pustular Psoriasis

Pustular psoriasis is an uncommon form of psoriasis consisting of widespread pustules on an erythematous background, as shown in the image below.

Pustular psoriasis may result in an erythroderma. Cutaneous lesions characteristic of psoriasis vulgaris may be present before, during, or after an acute pustular episode.

Types of pustular psoriasis

Generally, pustular psoriasis may be classified into several types depending on the clinical course, which may be acute, subacute, or chronic.

The acute, generalized type, accompanied by fever and toxicity, is also termed the von Zumbusch variant. This form of pustular psoriasis may be lethal if proper supportive measures are not taken during the acute phase.

An annular or circinate type that tends to run a subacute or chronic course with less systemic manifestations also has been described.

In addition, a juvenile or infantile type of pustular psoriasis is seen, but it is the least common form.

For patient education information, see eMedicine's Psoriasis Center, as well as Psoriasis, What Is Psoriasis?, Types of Psoriasis, Plaque Psoriasis, and Understanding Psoriasis Medications.

Enhanced polymorphonuclear leukocyte (PMNL) chemotaxis is much more pronounced in pustular psoriasis than in psoriasis vulgaris.^[1] This observation has been attributed to either an intrinsic PMNL defect or to the presence of chemoattractants in the psoriatic epidermis. Although the principal stimulus that triggers the phenomenon of massive PMNL migration from the vasculature to the epidermis is unknown, cytokines elaborated by keratinocytes are believed to aid the process.

Electron microscopic studies have shown the presence of basal keratinocyte herniations. These are cytoplasmic processes from basal keratinocytes that protrude into the dermis through gaps in the basal lamina in lesions of pustular psoriasis. These herniations mostly are clustered over collections of neutrophils in the dermis. This finding suggests an increased production of neutrophilic proteolytic enzymes in the dermis of these patients.

Immunohistochemical methods have determined the involvement of some of these proteases and their inhibitors in the development of pustulation.

Elastase is a proteolytic enzyme released by PMNLs during the process of extravasation and migration through the dermoepidermal junction. An epidermal elastase inhibitor, termed skin-derived antileukoproteinase, was found expressed in psoriatic skin prior to influx of PMNLs and to disappear when the composition of the infiltrate changed. This finding was not confirmed by other studies.

Additional studies investigating other potential mechanisms have shown decreased natural killer cell activity in generalized pustular psoriasis. An increased incidence of HLA-B27 also has been found among patients with pustular psoriasis. This haplotype is seen in psoriasis patients with peripheral arthritis, as well as in patients with ankylosing spondylitis and reactive arthritis.

A homozygous missense mutation in a gene that encodes an anti-inflammatory cytokine, an interleukin-36-receptor antagonist, has been associated with autosomal recessive inherited generalized pustular psoriasis. Presence of the mutation is associated with unopposed release of inflammatory cytokines, leading to pustular psoriasis.^[2]

Risk factors

The following factors can reportedly trigger an eruption of pustular psoriasis:

• Withdrawal of systemic steroids^[3]
• Drugs, including salicylates, iodine, lithium, phenylbutazone, oxyphenbutazone, trazodone, penicillin, hydroxychloroquine, calcipotriol, interferon-alpha, and recombinant interferon-beta injection^[4]
• Strong, irritating topicals, including tar, anthralin, steroids under occlusion, and zinc pyrithione in shampoo
• Infections^[5]
• Sunlight or phototherapy
• Cholestatic jaundice
• Hypocalcemia
• Idiopathic in many patients

Prevalence of pustular psoriasis

Pustular psoriasis is uncommon in the United States. The prevalence of pustular psoriasis in Japan is 7.46 cases per 1 million people.

Race predilection

Pustular psoriasis affects all races.

Sex predilection

The male-to-female ratio for pustular psoriasis is 1:1 in adults and 3:2 in children.

Age predilection

The average age among adult patients with pustular psoriasis is 50 years.

Children aged 6 weeks to 10 years can be affected, although rarely. One case report describes generalized pustular psoriasis in a 6-week-old infant.^[6]

Complications and morbidity in pustular psoriasis

Occasionally, acute respiratory distress syndrome may complicate generalized pustular psoriasis.

Other complications in pustular psoriasis may include the following:

• Secondary bacterial skin infections, hair loss (telogen effluvium), and nail loss
• Hypoalbuminemia secondary to loss of plasma protein into tissues
• Hypocalcemia
• Renal tubular necrosis as a result of oligemia
• Liver damage as a result of oligemia and general toxicity
• Malabsorption and malnutrition

Death in pustular psoriasis may occur as a result of cardiorespiratory failure. This usually happens only in untreated patients.

In the generalized type of pustular psoriasis, the skin initially becomes fiery red and tender. The patient experiences constitutional signs and symptoms, such as headache, fever, chills, arthralgia, malaise, anorexia, and nausea. Within hours, clusters of nonfollicular, superficial, 2- to 3-mm pustules may appear in a generalized pattern.

The most common sites of involvement for pustular psoriasis are the flexural and anogenital areas. Less often, facial lesions occur. Pustules may appear on the tongue and develop subungually, resulting in dysphagia and nail shedding, respectively.^[7] These pustules coalesce within 1 day to form lakes of pus that dry and desquamate in sheets, leaving behind a smooth, erythematous surface on which new crops of pustules may appear.

These episodes of pustulation may occur for days or weeks, thereby causing the patient severe discomfort and exhaustion. A telogen effluvium type of hair loss may develop in 2-3 months.

Upon remission of the pustular component, most systemic symptoms disappear; however, the patient may be in an erythrodermic state or may have residual lesions of psoriasis vulgaris.

The circinate or annular type of pustular psoriasis predominates in infancy. This subtype tends to run a more subacute or chronic course, with less severe manifestations. Often, recurrent episodes of annular or circinate erythematous plaques are seen, with pustules on the periphery. These lesions appear primarily over the trunk, but they also involve the extremities. They undergo peripheral expansion and central healing. Other systemic signs and symptoms are either absent or mild.

The juvenile/infantile type of pustular psoriasis typically has a benign course. Systemic involvement is not common, and spontaneous remissions occur frequently.

The patient appears frightened, often tachypneic, tachycardic, and febrile. The oropharyngeal mucosa may be hyperemic, and a geographic tongue or fissured tongue may be appreciated. The skin shows a generalized or patchy erythema studded with interfollicular pustules that may have an annular or nonspecific configuration. Flexural and anogenital accentuation may be present.

The lesions may appear on the trunk, extremities, and, rarely, on the face. Pustulation also occurs on the nail beds, resulting in onychodystrophy, onycholysis, and defluvium unguium.

Scaling may be observed, especially in areas that already have undergone pustulation. The rest of the physical examination depends on complications in other organ systems, such as the cardiovascular system.

The following conditions can mimic the symptoms of pustular psoriasis:

• Subcorneal pustular dermatosis
• Acute generalized exanthematous pustulosis (drug eruption)
• Gram-negative septicemia
• Infected generalized atopic dermatitis and/or seborrheic dermatitis

The patient’s complete blood count (CBC) reveals absolute lymphopenia coinciding with polymorphonuclear leukocytosis up to 40,000/µL.

In addition, the erythrocyte sedimentation rate is elevated, and the serum chemistry shows increased plasma globulins and decreased albumin, calcium, and zinc. If the patient is oligemic, then BUN (blood urea nitrogen) and creatinine also are increased.

If renal tubular necrosis occurs, urinalysis may show albumin and casts.

The culture and sensitivity of a pustule's contents prove negative, as do blood cultures. Loss of the cutaneous barrier to infection may result in bacteremia. Tzanck preparation and viral culture are negative.

Epidermal changes are similar to those in psoriasis vulgaris, with parakeratosis and elongation of rete ridges. The upper dermis shows a mononuclear infiltrate and numerous neutrophils migrating from papillary capillaries to the epidermis. Those already in the epidermis are arranged in a network of degenerated and flattened keratinocytes, forming a macropustule that is the characteristic histologic lesion and is termed the spongiform pustule of Kogoj.^[8]

Patients with the generalized form of pustular psoriasis eruption often are admitted to the hospital to ensure adequate hydration, bed rest, and avoidance of excessive heat loss. Treatment with bland topical compresses and saline or oatmeal baths assists in soothing and debriding affected areas. This topical strategy is effective as the sole therapy in many pediatric patients.

Start systemic medications together with the proper supportive measures. Oral retinoids, methotrexate, cyclosporine, 6-thioguanine, and hydroxyurea have been used with success.^{[9, 10, 11]} One case report described successful therapy with cyclosporine for pustular psoriasis during pregnancy.^[12]

Novel systemic therapies, such as biologics (eg, alefacept, etanercept, infliximab), have been used successfully in some cases of pustular psoriasis. Guidelines regarding their use in this type of psoriasis are needed, because some anecdotal reports describe paradoxical induction of pustular psoriasis by some of these biologics.^[13]

One case report describes successful infliximab treatment (5 mg/kg) of pustular psoriasis in a pregnant woman. The woman delivered a healthy female baby via cesarean. The neonate breastfed for 1 month and developed normally. No detectable adverse effects were noted in the neonate, despite potential exposure to infliximab throughout gestation and breastfeeding.^[14]

Other therapies, such as the use of topical calcineurin inhibitors (eg, tacrolimus, pimecrolimus), have also been shown to be effective in some cases of pustular psoriasis localized to the palms and soles. One case report described effective treatment of palmoplantar pustular psoriasis using adalimumab. An example of the palmoplantar condition is seen below.^[15]

Oral psoralen plus UV-A

Patients usually are too toxic and too erythrodermic during a flare to tolerate oral psoralen plus ultraviolet-A (PUVA).

However, some studies have shown that PUVA may be a safe and effective treatment in controlling flares of pustular psoriasis in pediatric patients, as well as in adults. Typically, PUVA is started once the patient has been stabilized on acitretin.

UV-B and narrow-band UV-B

While the literature is scant regarding the use of phototherapy for pustular psoriasis,^[16] narrow-band UV-B may be a reasonable choice, since it has achieved therapeutic results similar to those of PUVA in other forms of psoriasis.

Retinoid plus PUVA

Acitretin is administered first at 0.2-0.5 mg/kg for 7 days, and then PUVA is added 3 times per week. Upon clearance, acitretin can be withdrawn, and maintenance phototherapy with PUVA or, preferably, narrowband UVB can be continued as needed.

Request consultations with medical subspecialists according to the degree of systemic involvement.

Older patients with von Zumbusch-type of pustular psoriasis have a poor prognosis.

Death can result from cardiorespiratory failure during the acute erythrodermic stage.

Patients with chronic psoriasis vulgaris prior to a generalized pustular episode tend to have a better prognosis than do patients with more atypical forms of psoriasis prior to the pustular flare.

In children, as long as serious secondary infections are avoided, episodes of pustular psoriasis have a good prognosis.