Discoid eczema, also known as nummular dermatitis, is a type of eczema/dermatitis presented by well-defined, scattered, coin-shaped, and coin-sized plaques of eczema.
The cause of discoid eczema remains unknown. However, some cases have been associated with Staphylococcus aureus infection. The eruption can be triggered by contact dermatitis, a localised injury (i.e., insect bite, thermal burn, or scratch), dry skin, or varicose veins.
Discoid eczema can affect all age groups. It is more prevalent among older adult males and younger adult females. In males, this type of eczema is often linked with chronic alcoholism. Drug-induced discoid eczema can be caused by medications that result in skin dryness. Moreover, discoid eczema can occur in association with eczema craquelé, atopic eczema, and secondary eczematisation.
Discoid eczema usually affects limbs, mainly legs, however, the rash can spread throughout the entire body. The distribution is usually bilateral, but in cases with varicose veins, it can be asymmetrical.
This condition has two clinical forms: exudative acute discoid eczema and dry discoid eczema. Exudative acute discoid eczema is characterized by oozy papules, plaques, and blisters. Dry discoid eczema is characterized by subacute or chronic erythematous, dry plaques.
Individual plaques appear well-circumscribed, 1-3 cm in diameter, and inflamed. These patches are round or oval. Many patients report itchiness, irritation, and dryness.
Severe discoid eczema can appear all over the body as small and large itchy plaques due to autoeczematisation reaction.
Patches can clear up without leaving any signs. In dark skin, these patches may persist as dark brown postinflammatory hyperpigmentation or pale postinflammatory hypopigmentation.
In most cases, discoid eczema can be diagnosed due to its defined clinical features. Bacterial swabs may be done to reveal Staphylococcus aureus colonisation or infection. Patch testing can be administrated if is believed that chronic discoid eczema is a result of contact allergy to metals like nickel and chromate.
As discoid eczema is associated with loss of skin barrier function, it is vital to protect the skin from injury, apply emollients on daily basis, and avoid allergens.
This type of dermatitis is often linked with minor skin injuries, so it is highly recommended to protect the skin. For example, if hands are affected, gloves should be worn to avoid skin getting irritated by detergents, friction, solvents, excessive water, or other chemicals.
The application of emollients can be done by using moisturising creams, soap substitutes, and bath oils. These methods help to relieve scaling, dryness, and itching, which are very common for dermatitis. Emollients should also be applied to unaffected skin to reduce dryness.
If contact allergy has been identified by patch testing, exposure to this allergen should be avoided.
Anti-inflammatory treatments include using topical steroids and/or taking antibiotics. Other treatments like oral antihistamines, ultraviolet (UV) treatment, steroid injections, and other steroids can be prescribed for severe discoid eczema.
Discoid eczema can be a chronic condition which often relapses during cold winter months. Many cases tend to resolve with time.
Centre for Medical and Surgical Dermatology offers unique and personalized treatment options for discoid eczema for each patient.
