Discoid eczema, or discoid dermatitis, is an inflammation of the skin. A rash appears that looks like red coin-shaped discs, or plaques of eczema. It is extremely itchy and uncomfortable.
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.