Generalised pustular psoriasis

What is generalised pustular psoriasis?

Generalised pustular psoriasis is a rare and serious skin disorder that presents with flares of widespread sterile pustules on a background of red and tender skin. It is also known as acute generalised pustular psoriasis of von Zumbusch.

Related pustular disorders include:

• Subcorneal pustular dermatosis
• Acute generalised exanthematous pustulosis (AGEP)
• Palmoplantar pustulosis (hands and feet)
• Acrodermatitis continua of Hallopeau (pustulosis of digits).

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What causes generalised pustular psoriasis?

Generalised pustular psoriasis is an inflammatory skin disease. Recent research suggests generalised pustular psoriasis is distinct from psoriasis, with a different pattern of immune activation. Generalised pustular psoriasis has been associated with abnormalities in the cytokine (messenger protein) interleukin -36-receptor-antagonist signalling. This is due to recessive IL36RN gene mutations. These mutations are also found in some patients with AGEP, palmoplantar pustulosis and acrodermatitis continua of Hallopeau.

About 10% of patients with generalised pustular psoriasis have a preceding history of psoriasis, in which there are persistent, circumscribed, red and scaly plaques. In these patients, CARD14 gene gain-of-function abnormalities have been reported.

Possible trigger factors for flares of generalised pustular psoriasis may include:

• Sudden withdrawal of injected or oral corticosteroids
• Drugs such as lithium, aspirin, indomethacin, iodide and some beta-blockers
• Infection.

Generalised pustular psoriasis sometimes arises in pregnancy. Previously known as impetigo herpetiformis, this name is no longer favoured because the eruption has nothing to do with either impetigo (a bacterial infection) or herpes simplex (a viral infection).

Strong, irritating topical preparations such as coal tar, dithranol and withdrawal of strong topical corticosteroids can lead to localised areas of pustulosis, often associated with existing plaques of psoriasis.

What are the signs and symptoms of generalised pustular psoriasis?

Generalised pustular psoriasis is characterised by recurrent acute flares.

• Initially, the skin becomes dry, fiery red and tender.
• Within hours, 2–3 mm pustules appear.
• After a day, the small pustules coalesce to form lakes of pus
• These dry out and peel to leave a glazed, smooth surface on which new crops of pustules may appear.
• Successive crops of pustules may appear and erupt every few days or weeks.

Systemic symptoms

Flares of generalised pustular psoriasis may result in:

• Fever and chills (or hypothermia)
• A headache
• Rapid pulse rate
• Loss of appetite and nausea
• Thirst and dehydration
• Muscle weakness
• Leg swelling.

Remission occurs within days or weeks and the skin reverts to its previous state or erythroderma may develop. Relapses are common.

How is generalised pustular psoriasis diagnosed?

Generalised pustular psoriasis is often suspected clinically by experienced dermatologists. However, the following tests are usually undertaken to confirm the diagnosis and to identify potential complications.

• Laboratory tests for bacterial infection
• Skin biopsy, which shows superficial (subcorneal) pustules and neutrophilic infiltration on histopathology
• Blood count
• Kidney and liver function
• Electrolytes, calcium / phosphate

What are the complications of generalised pustular psoriasis?

Death can result from cardiorespiratory failure during the acute eruptive phase of generalised pustular psoriasis, so it is essential to treat it as early as possible. Older patients are at highest risk. Other complications include:

• Secondary bacterial infection
• The blood count may show anaemia, neutrophilia, lymphopenia
• Raised inflammatory markers such as C-reactive protein (CRP)
• Disturbed protein and electrolyte balance, low albumin, low calcium and low zinc
• High-output cardiac failure
• Renal and liver impairment
• Protein-losing enteropathy
• Peripheral neuropathy
• Malabsorption of nutrients and therapeutic drugs.

What treatment is available for generalised pustular psoriasis?

Generalised pustular psoriasis can be life-threatening, so hospitalisation is usually required. The aim is to prevent further fluid loss, stabilise body temperature and restore electrolyte imbalance. Specialist care is essential.

Affected areas are treated with bland topical compresses using emollients and low potency topical steroid creams.

Systemic medications may include:

• Antibiotics for confirmed or suspected infection
• Acitretin
• Systemic corticosteroids (cautiously)
• Ciclosporin (cautiously)
• Methotrexate
• Colchicine
• Biologic agents including infliximab, etanercept, ustekinumab, adalimumab, and anakinra.

Anti-IL36 monoclonal antibodies are being evaluated for their effectiveness in generalised pustular psoriasis.