Nummular dermatitis (aka discoid eczema) has an incidence of 2 in 1000 people, mostly men in the age range of 55-65. However, treatment with a TNF-inhibitor is also a risk factor.
Like many medical terms, the name nummular dermatitis comes from Latin roots:
- nummular – from nummus – coin
- dermis – a layer of skin
- itis – inflammation
So, nummular dermatitis is coin-shaped inflamed patches of skin. This rash can itch and burn, even to the extent that it disrupts sleep. Some people, however, are fortunate enough to skip the unpleasant sensations that typically accompany this unsightly rash (sometimes there are advantages to peripheral neuropathy).
This rash is not contagious.
Nummular dermatitis begins as a group of blisters or tiny red dots. It quickly becomes a round or oval-shaped patch of red (sometimes pink or brown) skin. Multiple patches are possible; they can be as small as two millimeters, or as large as four inches. The rash usually appears on the extremities (arms, legs, feet, hands) or torso. Thankfully, it is rare for patches to appear on the face.
This rash is unique in appearance and can often be diagnosed based on a visual examination. Usually no expensive tests are needed, but occasionally the rash will look like ringworm, in which case a doctor might need to take a sample to make an accurate diagnosis.
There are no known causes of nummular dermatitis, however a Dutch study of RA patients done in 2005 showed that 25% of RA patients on TNF-inhibitors needed referral to a dermatologist, vs. 13% of RA patients who had never taken a TNF-inhibitor. Fortunately, only a small number had nummular dermatitis. Of note, hepatitic C patients treated with a TNF-inhibitor have an increased risk of nummular dermatitis. It will be interesting to see the results of follow-up studies now that TNF-inhibitor use is more common in the treatment of RA.
Home treatments aren’t enough to deal with nummular dermatitis. Without adequate treatment, this rash can stick around indefinitely. Even with medical treatment, the rash can take months to resolve – some sources say it sometimes takes a full year for the rash to go away.
The goal of treatment is to:
- reduce inflammation
- repair the skin
- rehydrate the skin
- if infected, treat the infection
To reduce inflammation, prescription-strength steroid cream or ointment can be rubbed into the rash two-three times daily. Unless you are Gumby, if your rash is on your back, you will need assistance with the application. Oral steroids can be used when topical steroids are ineffective (this also eliminates the need for an assistant).
To increase absorption, the steroid cream/ointment should be applied to wet skin – particularly after a shower or twenty-minute soak. Following application of the topical medicine, a good moisturizer should be applied to wet skin. Some people recommend covering the medicated areas (ie with plastic wrap) for an hour to hold in the moisture. Gently pat yourself dry; do not rub with a towel and remove the steroid cream & moisturizer.
Another treatment option – when topical steroids fail – is light therapy (UVB).
Although home treatments alone can’t cure nummular dermatitis, there are a few things you can do. Take good care of your skin and be sure to moisturize it well. Also, avoid potential flare-triggers.
A few of the things that sometimes cause flare-ups of this condition are:
- frequent use of detergents or harsh soaps
- hot tub usage
- extreme temperatures (very hot or very cold)
- extremes in humidity (or lack thereof)
- rough wool clothing
- skin injury (ie cut, burn, or insect bite)
- some medications (examples include accutane, neomycin, and TNF-inhibitors)
- sensitivity or allergy to rubber, nickel, cobalt, formaldehyde, or mercury
This means that if your routine is to take a long, hot shower first thing in the morning before dressing in a nice warm, wool sweater and cozy wool socks, you might need to modify your routine. Make it a shorter lukewarm shower, apply a good moisturizer to your skin, then dress is loose cotton clothing. If your workout routine later includes spending twenty minutes in a steam room, followed by half an hour soaking/stretching in a hot tub, followed by an hour in a swimming pool, ten minutes in the dry sauna, and then another hot shower, you’re intentionally doing five of the eight things you need to avoid.
See a doctor for accurate diagnosis and treatment if you suspect nummular dermatitis.
Vocabulary for Reading Medical Literature about Nummular Dermatitis
erythematous – red
papules – bumps
vesicles – very small blisters
pruritic – itchy
xerosis – abnormal dryness
Arthritis Research & Therapy
American Academy of Dermatology
British Association of Dermatologists