It is also known as nummular dermatitis or nummular eczema, after the Latin word "nummulus," meaning a coin.
The plaques affect different parts of the body, but mostly the lower legs, hands, and forearms, and sometimes the trunk. The face and scalp are not affected.
Discoid eczema is a chronic condition, which means that it is long-term or recurrent. It is not contagious, and it cannot be caught by touching an affected person or being near them.
According to the American Academy of Dermatology (AAD), men are more likely to have it than women, and it tends to appear between the ages of 55 and 65 years. Women who get it are normally younger, starting form the teenage years or young adulthood.
Discoid eczema is an itchy and uncomfortable skin rash.
Moisturizing with emollients is the main treatment for discoid eczema. A number of over-the-counter (OTC) preparations are available, but if these do not work, a doctor may offer another solution.
The Merck Manuals note that an occlusive dressing impregnated with flurandrenolide is available for use during the night.
If less aggressive treatments do not work, oral steroids may be prescribed. Steroid injections may help against stubborn lesions. Steroids should always be used sparingly, and according to the physician's instructions.
A physician may also prescribe antibiotics, such as tetracycline, to treat secondary infections.
If lesions are slow to heal, permanent brown blemishes, known as macules, may remain, especially on the legs.
The causes are unknown, but it is more likely to affect people who have dry, sensitive skin that is easily irritated by soap, detergents, and rough clothing.
Discoid eczema appears to be more common during the winter months, when indoor humidity levels are lower.
People with discoid eczema may also have atopic eczema.
Poor blood flow may worsen symptoms on the lower legs.
It may be linked with the use of certain medications, notably interferon and isotretinoin, used to treat acne.
The round or oval plaques consist of tiny, raised, red spots and scaling on a red base with well-defined edges. The patches can range in size from 2 to 10 centimeters in diameter, and a person may have between one and 50 of them.
The affected areas are red, and they have well-defined edges. On top of the coin-shaped plaques, there may be small scales or yellowish crusts.
There may be pus and weeping, a sign of a staphylococcal, or bacterial, infection. They eventually dry and become scalier, sometimes with a clear center.
The affected areas are extremely itchy, especially at night, and they may burn or sting.
Constant scratching and rubbing can lead to a process of lichenification, in which the epidermis, or outer layer of skin, becomes overgrown. This causes the skin to thicken, and exaggerated skin markings appear, making the skin look like leathery bark.
Is it ringworm?
Ringworm refers to a group of fungal infections, including athlete's foot. One type, tinea corporis, may resemble discoid eczema.
While ringworm is a fungal infection, the cause of discoid eczema is unknown. It is more likely to affect people with very dry skin. Ringworm can affect any type of skin.
Discoid eczema starts as very small, red spots that turn into a rash. Ringworm is a circular patch that grows and becomes lighter in the middle, forming a ring. A number of rings may form across the body. Both rashes can itch, but discoid eczema can cause a burning sensation.
A doctor should look at the rash, as a correct diagnosis will make appropriate treatment possible.
There is no cure, but treatment can help relieve symptoms by rehydrating the skin, treating inflammation, and preventing repeat infections.
Treatment focuses on rehydrating the skin.
Patients with discoid eczema may find it useful to:
- bathe or shower once a day in cool or lukewarm water
- moisturize the skin twice daily and after showering, while the skin is damp, using medicated moisturizers to help to seal the water in the skin
- practice good hand hygiene, keeping hands clean and nails clean and short to prevent infection
- avoid scratching or rubbing the lesions to prevent permanent scars and infections
- apply topical steroids directly onto the skin to reduce inflammation
- use tar preparations to reduce inflammation in older, thickened, scaly plaques
- try to stay in a cool, moist, environment, and avoid hot, dry surroundings that make symptoms worse
- use an emollient cream, lotion, or soap substitute to soften and smooth the skin and to keep it supple and moist
- moisturize skin to prevent cracking and irritation.
- use wet wraps, such as dampened bandages, to relieve inflamed patches, possibly with diluted steroids or emollients added to them
If commercial products do not work, a doctor or pharmacist can advise about alternatives. There are over-the-counter (OTC) medications available, including shampoos, emollient products, and some low-dose topical steroids.
Controlled, limited exposure to natural sunlight may help, but the heat may make the itching worse.
Artificial ultraviolet A (UVA) or ultraviolet B (UVB) light therapy may be used, but this must be carefully controlled because of the risk of premature skin aging or skin cancer.
Complementary treatments for patients with atopic eczema and discoid eczema include aromatherapy, massage, homeopathy, and some herbal remedies.
Before using any complementary or alternative therapy, patients should check with a physician and ensure the treatment is backed by research and comes from a reputable source. Patients should also inform their doctor about all complementary treatments they are taking.
A physician may diagnose discoid eczema after seeing the hallmark signs and symptoms, and they may refer the patient to a dermatologist, or skin specialist.
Samples or scrapings of lesions may be taken for analysis and to rule out ringworm.
If there appears to be a secondary infection, the doctor will take a swab for analysis.
Here are some tips that may help reduce the chance of discoid eczema coming back:
- Hydrate the skin by using moisturizers and adding oils to the bath.
- Pat the skin dry gently with a soft towel, after bathing.
- Wear loose clothing that does not irritate the skin, and choose natural, rather than man-made fabrics.
- Try an air humidifier in the home.
- Use a laundry detergent that is not irritant to skin and double rinse to remove harmful chemicals which may remain on the laundry.
- Follow the doctor's instructions and recommendations carefully.
- Avoid hot baths or showers
- Do not use soaps
- Refrain from scratching or rubbing the skin.