Author: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997. Updated July 2014.
Discoid eczema is a common type of eczema/dermatitis, in which there are scattered, roundish plaques of eczema. Eczema can be intensely itchy. Discoid eczema is also called nummular dermatitis.
The cause of discoid eczema is unknown. Some cases are associated with Staphylococcus aureus infection.
The eruption can be precipitated by:
Discoid eczema can affect children and adults. It is slightly more common in adult males than females. In males over the age of 50 years, there is an association with chronic alcoholism.
There are two forms of discoid eczema:
Both forms of discoid eczema usually affect the limbs than the trunk, but the rash may be widespread. Although often bilateral, the distribution is often asymmetrical.
Individual plaques are well circumscribed, mostly 1–3 cm in diameter, and inflamed. The majority of patches are round or oval, hence the name ‘discoid‘ or ‘nummular’ (coin shape). The plaques are usually very itchy but sometimes don't itch at all. The skin between the patches is usually normal, but may be dry and irritable.
Severe discoid eczema may generalise, with numerous small to large itchy lesions appearing all over the body due to an autoeczematisation reaction.
The patches may clear up without leaving a sign. However, in darker skins, marks may persist for months. These may be dark brown (postinflammatory hyperpigmentation) or paler than surrounding skin (postinflammatory hypopigmentation).
In most cases, the appearance of discoid eczema is quite characteristic.
As discoid eczema is associated with loss of skin barrier function, it is important to:
Protect the skin from injury.
As this type of dermatitis often starts off as minor skin injuries, protect all your skin carefully. If the hands are affected, use gloves and tools to make sure the skin is not irritated by friction, detergents, solvents, other chemicals or excessive water.
Apply emollients frequently
Emollients include bath oils, soap substitutes and moisturizing creams. They can be applied to the dermatitis as frequently as required to relieve itching, scaling and dryness. Emollients should also be used on the unaffected skin to reduce dryness. It may be necessary to try several different products to find one that suits. Many people find one or more of the following helpful: glycerine and cetomacrogol cream, white soft paraffin/liquid paraffin mixed, fatty cream, wool fat lotions.
Anti-inflammatory treatments include:
Topical steroids are anti-inflammatory creams or ointments available on prescription which may clear the dermatitis and reduce irritation. The stronger products are applied to the patches just once or twice daily for 2–4 weeks. They are repeated from time to time. Mild ones such as hydrocortisone are safe for daily use if necessary.
Antibiotics (most often flucloxacillin) are often prescribed if the dermatitis is blistered, sticky or crusted. Sometimes discoid eczema clears completely on oral antibiotics, only to recur when they are discontinued.
Other treatments sometimes prescribed for severe discoid eczema include:
Antihistamine pills may reduce the itching, and are particularly helpful at night-time. They do not clear the dermatitis. Non-sedating antihistamines appear less useful for discoid eczema than first-generation antihistamines taken at night to help sleep.
Ultraviolet radiation (UV) treatment
Phototherapy several times weekly for 6–12 weeks can reduce the extent and severity of discoid eczema.
Intralesional steroids are sometimes injected into one or two particularly stubborn areas of discoid eczema. This treatment is unsuitable for multiple lesions.
Systemic steroids are reserved for severe and extensive cases of discoid eczema. They are usually prescribed for a few weeks while continuing steroid creams and emollients on residual dermatitis.
Other oral treatments
Persistent and troublesome discoid eczema is occasionally treated with methotrexate, azathioprine or ciclosporin. These medicines have important risks and side effects and require careful monitoring by a specialist dermatologist. They may be more suitable in many cases than long-term steroids.
Discoid eczema can usually be controlled with the above measures, although it has a tendency to recur when the treatment has been stopped. In most patients, discoid eczema eventually clears up completely.
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