63 - sneddon-wilkinson disease (Subcorneal pustular dermatosis)

Subcorneal pustular dermatosis

Subcorneal pustular dermatosis is also known as Sneddon-Wilkinson disease. It is a rare condition, characterised by pustules that appear in crops over months or years.

In some cases, subcorneal pustular dermatosis may be later diagnosed as generalised pustular psoriasis ; generalised pustular psorasisis tends to be a more serious condition.

Also known as:
Duhring-Sneddon-Wilkinson syndrome
Sneddon syndrome

Associated persons:
Louis Adolphus Duhring
Ian Bruce Sneddon
Daryl Sheldon Wilkinson

Description:
Chronic recidivating pustulous dermatosis of unknown origin with eruptions usually involving the axillae, groins, abdomen, submammary areas, the flexor aspects of the limbs, and, less commonly, the palms and soles. The course is quite similar to that of dermatitis herpetiformis, but there is rarely itching. Predominantly in women (4: 1); onset after 40 years of age. Seldom in children.

What does it look like?

Subcorneal pustular dermatosis is characterised by numerous soft pustules at the skin surface. They usually appear on the trunk, particularly in the skin folds such as the armpits and groin. They may appear on otherwise normal skin, but there are often within a red patch. The pustules resolve over a few days and are replaced by fine scale before there is another relapse and new pustules form again. The lesions are sometimes itchy, but generally the patient is otherwise well. It may flare-up for a few weeks and then clear up for months or years before reappearing. The process may be repeated over many years.

Subcorneal pustular dermatosis affects women more often than men and generally occurs in people over the age of forty.

Subcorneal pustular dermatosis

What is the cause of subcorneal pustular dermatosis?

The cause of subcorneal pustular dermatosis is not known.

However, it is associated with some other conditions. The most frequent are:

• IgA monoclonal gammopathy (accumulation of abnormal proteins in the blood)
• Multiple myeloma
• pyodermal gangrenosum
  

Other less frequent associated conditions include RA , SLE ,HYPOTHYROIDISM AND HYPERTHYROIDISM, polycythemia rubra vera, and SAPHO SYNDROME (synovitis, acne, pustulosis, osteitis).

Subcorneal pustular dermatosis can be very difficult to distinguish from generalised pustular psoriasis and acute generalised exanthematous pustulosis. They appear to be closely related disorders.

Investigations

Often, a skin biopsy will be performed to confirm the diagnosis.

Blood tests are likely to include a general screen such as blood count, calcium levels and liver function tests, and protein electrophoresis to look for a gammopathy.

Treatment

Treatment is aimed at preventing complications. dapsone is often successful, with the lesions resolving over a month. Ongoing maintenance with a lower dose is sometimes needed.

Other treatment options include:

• Sulfapyridine or sulfamethoxypyridazine (not available in New Zealand)
• acitretin
  

• phototherapy including UVB and PUVA
• COLCHICINE
  
• ciclospirin or other immune suppressants such as mycophentolate mofenil
• biological response mediators including infliximab and adalimumab

Miscellaneous other agents have been successfully used for individual patients.systemic steroids are generally ineffective and may in fact precipitate a flare-up of subcorneal pustular dermatosis.

Patients need long term follow-up with periodic evaluation of serum protein electrophoresis and immunophoresis because paraproteinemia or myeloma may develop after several years.