Nummular eczema is a puzzling disease with at least three names: (1)
nummular eczema, the most commonly used name, (2) nummular
eczematous dermatitis, a longer and more medically descriptive name,
and (3) discoid eczema, a name derived from the disease’s typical
coin-shaped lesions seen in this photo:
Typical coin-shaped lesions
of nummular eczema on the back of a patient’s hand.
(Photos used with permission of the
American Academy of Dermatology
National Library of Dermatologic Teaching Slides)
The cause or causes of nummular eczema
are not known with certainty, but many different causes have been
suggested. A number of factors, acting alone or in combination, may
be suspected—for example, dry skin in indoor and outdoor
environments with low humidity; isotretinoin (a prescription
medication used to treat severe acne that proves resistant to other
treatments); and bacterial
infections that induce a hypersensitivity reaction in skin.
Factors that may cause worsening of
nummular eczema include wool clothing worn next to the skin, topical
medications, soaps and detergents, and frequent bathing (as seen in
Red, crusted nummular eczema
lesions on the ankle of a patient who
bathed with vigorous rubbing several times a day.
Nummular eczema characteristically
appears first as a group of tiny red spots (papules) and
blister-like lesions (vesicles) that enlarge and merge into a
reddened, itchy, sometimes burning coin-shaped lesion two to 10
centimeters in diameter. The lesion may be uniformly red at first,
then clear in the center to form a "ring" that resembles the fungal
infection called ringworm.
New, acute lesions are likely to "weep"
edematous fluid that dries into crusts. Chronic, persisting lesions
An outbreak of nummular eczema may
begin with one or several lesions. Some patients experience
spontaneous clearing of lesions within a year. In other patients the
lesions persist or recur for many years; lesions that recur after
clearing tend to do so at the sites of the original outbreak.
The most common sites for nummular
eczema are the legs (most common), arms and hands, and the torso.
The disease is more frequent in men than in women, with a peak age
of onset at 55 to 65 years. A smaller peak has been observed in
women 15 to 25 years old.
Since the cause of nummular eczema is
unknown, treatment is largely directed at relief of the major
symptoms of itching and burning. Treatment should be prescribed by a
dermatologist after a diagnosis of nummular eczema is confirmed.
Baths with oil additives, and regular application of emollients can
keep the skin from becoming excessively dry. Tar preparations and
topical anti-inflammatory steroid agents may be prescribed to reduce
inflammation and itching. Skin infection may be treated with
prescribed antibiotics. Anti-histamines or ultraviolet phototherapy
may be prescribed. Oral steroids may also be prescribed in severe
cases that are resistant to other forms of treatment.
Sotor NA. Nummular
eczematous eczema. In: Freedberg IM et al (eds.) Fitzpatrick’s
Dermatology in General Medicine, 5th ed. New York: McGraw
Jarvikallio A, Naukkarinen A, Harvima
IT et al. Quantitative analysis of tryptase- and chymase-containing
mast cells in atopic dermatitis and nummular eczema. Br J Dermatol
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