Pustular Psoriasis

Pustular psoriasis is an uncommon variation of psoriasis. Polymorphonuclear leukocyte chemotaxis appears to be rather more pronounced in this condition than in ordinary psoriasis but it is unclear if this is the cause or the result of the variant. There is some evidence that it may predispose to the disease.¹

The condition is uncommon. The average age of those affected is 50 but the range is wide and rarely it can affect children. No race is exempt. The sex ratio is equal although in the rare cases involving children, boys are affected slightly more often.

Precise figures on prevalence in the UK are not available. In children, it is so rare that the literature contains fewer than 200 cases.² Even for adults, reports are rarely of more than 10 patients from a single centre.³

Risk Factors

There appears to be an increased incidence in people who carry the HLA-B27 haplotype. They are also more susceptible to ankylosing spondylitis, seronegative arthritis and Reiter's disease.
The following have been recorded as likely precipitating factors:

• Drugs, including
  • salicylates
  • penicillin
  • iodine
  • lithium
  • some beta blockers
  • trazodone
  • hydroxychloroquine
  • calcipotriol
  • interferon,
• Corticosteroid withdrawal
• Potent, irritating topical medications, including
  • tar
  • anthralin
  • steroids under occlusion
  • zinc pyrithione in shampoo
• Sunlight or phototherapy
• Cholestatic jaundice
• Infections. Streptococcal infection is usually associated with guttate psoriasis but it has been associated with pustular psoriasis too.²
• Hypocalcaemia

In many patients there is no obvious precipitant.

The more common type is generalized pustular psoriasis. The acute generalized type accompanied by fever and toxicity also is termed the von Zumbusch variant.

• The skin becomes very red and tender.
• Symptoms include headache, fever, chills, arthralgia, malaise, anorexia, and nausea.
• The patient often looks anxious. There is a fast respiratory rate, tachycardia and pyrexia, suggesting a toxic state. The tongue is dry and cracked.
• Clusters of pustules appear within hours. They are superficial, 2 to 3mm in diameter and may appear in a generalized pattern.
• The flexural and anogenital regions are most commonly affected. Facial lesions are less common.
• Pustules may occur on the tongue and under the nails, causing dysphagia and loss of nails respectively.
• Within the next 24 hours, the pustules coalesce, dry and desquamate in sheets. The underlying skin that appears is smooth and erythematous but new crops of pustules may appear.
• These episodes of pustule formation may occur for days to weeks, leaving the patient uncomfortable and exhausted.
• 2 or 3 months later a telogen effluvium type of hair loss may develop.
• As the pustules remit, most systemic symptoms ebb too but the patient can be left with erythroderma or with residual lesions of ordinary psoriasis.

The circinate or annular type is more usual in infancy.

• It tends to run a more subacute or chronic course and to be less severe.
• There are often recurrent episodes of annular or circinate erythematous plaques, with pustules on the periphery.
• They are mostly over the trunk but also involve the extremities.
• They expand peripherally whilst healing in the centre.
• Systemic symptoms are mild or absent.
• The juvenile or infantile variation of pustular psoriasis is usually benign benign. Systemic features are uncommon, and spontaneous remissions are frequent.

Another variant is localised pustular psoriasis, which appears on the hands or feet and is also known as palmoplantar pustulosis. This is different from a localised form of generalised pustular psoriasis.

• Drug eruptions
• Septicaemia

• FBC shows a marked rise in neutrophils whilst lymphocytes are reduced. ESR is elevated. The white count may rise to 25,000 to 40,000 with a marked drop in the lymphocyte count. If this is noted and treatment can be started before the clinical disease, it may abort it.⁴
• Serum globulin is raised and albumin is low.
• Calcium and zinc levels are reduced.
• If there is a marked reduction in blood volume, renal function parameters will be abnormal with elevated creatinine and if renal tubular necrosis occurs, there will be casts in the urine.
• Cultures of pustules and blood cultures are negative.

The patient is usually so ill and the intensity of care is such that admission to hospital is required. This condition can threaten life.

• Adequate hydration must be maintained. This may require the intravenous route.
• Bed rest is recommended and if a substantial amount of skin is involved, loss of heat may be a problem.
• Bland topical compresses and saline or oatmeal baths assist in soothing and debriding affected areas. For children, this is often all that is required.
• Specific medications include:
  • oral retinoids, usually acetretin
  • methotrexate
  • cyclosporine
  • 6-thioguanine
  • hydroxyurea.
• The new biological therapies such as alefacept, etanercept and infliximab have been used with success at times.
• Topical calcineurin inhibitors such as tacrolimus and pimecrolimus have been effective in some cases of pustular psoriasis limited to the palms and soles.
• PUVA cannot normally be tolerated in the early stage, except perhaps in children who tend to experience a milder disease. Once the patient is stable, usually after several days of acetretin, then PUVA may be commenced. Results are good.⁴

The very new treatments have not been used extensively and the literature is still rather limited. This is partly due to the rarity of the disease. Therapeutic guidelines based on a scoring system have been suggested.³

• Secondary bacteria infection of the skin may occur.
• Hair loss with telogen effluvium is possible.
• If the subungual areas are involved, the nails will be lost.
• Hypoalbuminemia may result from loss of plasma protein into tissues.
• Hypocalcaemia.
• Reduced circulating volume may cause renal tubular necrosis.
• Poor circulation and general toxicity may cause liver damage.
• Malabsorption and malnutrition
• Death from cardio-respiratory failure is rare and usually in untreated patients. It trends to occur in the acute erythrodermic phase. Occasionally, acute respiratory distress syndrome may complicate generalized pustular psoriasis.

• Older patients with the von Zumbusch-type variant have a poor prognosis.
• Children tend to have a good prognosis unless there is secondary infection.
• If the pustular psoriasis was preceded by ordinary chronic psoriasis, the prognosis is better than if it was preceded by an atypical form.