Discoid eczema: Nummular eczema

Published on 18/03/2015 by admin

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Discoid eczema

Nummular eczema

Ian Coulson

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

image

Discoid eczema comprises relatively well-defined, usually multiple, coin-sized plaques. In the acute stages they often weep or ooze; in the chronic phase lesions are discrete, hyperkeratotic or lichenified. Itching is usual. It primarily affects the limbs (especially the legs), sometimes the trunk, and rarely the face or flexures.

Management strategy

Discoid eczema (nummular dermatitis) has many causes. It is usually idiopathic in older patients, but similar lesions may occur due to contact allergic reactions, as a pattern of hand and foot eczema, in atopic dermatitis (AD), as an ‘id’ eruption related to venous eczema, or locally (e.g., after trauma, insect bite reactions, ‘halo eczema’ around melanocytic nevi). Discoid eczema has been reported as a manifestation of drug reaction to gold, TNF antagonists, interferon, and retinoids (see below). Comparisons between studies may be limited if the site(s) and etiology are not stated, or represent a mixed spectrum.

There are few publications on the pathophysiology of discoid eczema to inform treatment. An association with dry skin (xerosis) is documented, and discoid lesions may appear during treatment with isotretinoin (which reduces sebum secretion). However, dry skin is not consistently present, and the morphology of discoid eczema differs from that of xerosis or asteatotic eczema.

One study suggested that patients with discoid eczema have a degree of xerosis similar to that of age-matched controls, but have stronger delayed hypersensitivity to allergens that permeate the skin as a result of scratching. A link with atopy has been proposed, but serum IgE levels are generally normal.

Occult infections (e.g., dental abscess) and infections causing dry skin (e.g., leprosy) have rarely been linked with discoid eczema. Helicobacter pylori has been implicated, but the evidence is weak.

It is difficult to provide specific therapeutic strategies because of the various different causes and the paucity of pertinent publications; most reports are retrospective from individual departments, or are anecdotal, rather than formal trials. The main therapeutic issues are:

image Other disorders may need to be excluded, especially mycoses, psoriasis, Bowen’s disease, mycosis fungoides, sarcoidosis.

image A medication and alcohol history should be taken.

image Patch testing may be useful; metals and medicaments (such as fusidic acid, lanolin, neomycin, and cetosteryl alcohol) are most implicated.

image The management of discoid eczema is generally similar to that of other eczemas; emollients appear to be helpful owing to the link with dry skin.

image The mainstay of treatment is topical corticosteroids. Severe itch in discoid eczema usually dictates that strong agents are applied; this is safe because the individual lesions are small, rarely affect thin skin sites such as the face or flexures, and usually respond to this approach. Chronic lichenified lesions may respond better to steroid impregnated tapes or by using a potent steroid with hydrocolloid dressing occlusion.

image Calcineurin antagonists have been used successfully both as monotherapy and in combination with topical steroids, but trials specifically looking at efficacy in discoid eczema exclusively, rather than atopic eczema generally, are lacking.

image If weeping is present, the use of soaks (with, e.g., 1 in 10 000 potassium permanganate solution) will help dry lesions up and prevent lesions sticking to clothes or dressings.

image Secondary impetigenization particularly in the exudative phase is common, and combining a topical antibiotic or antiseptic, or the use of an oral anti-staphylococcal antibiotic helps.

image Tar-based treatments and impregnated bandages to minimize the effects of scratching may help.

image Sedating antihistamines before retiring will help nocturnal scratching and minimize excoriation.

image Systemic immunosuppressive therapies are usually not required.

Specific investigations

First-line therapies

image Topical corticosteroids ± antibacterial agents C
image Emollients C
image Tar-based preparations C
image Oral antibiotics C
image Oral antihistamines C
image Topical doxepin A

Most of these are standard treatments for discoid eczema; however, in terms of evidence grading, most studies include a variety of different eczemas, few specifically identify results for discoid eczema, and no comparative trials have been identified.

The antipruritic effect of 5% doxepin cream in patients with eczematous dermatitis.

Drake LA, Millikan LE. Arch Dermatol 1995; 131: 1403–8.

Significant improvement in itch after 1 day, not at 7 days.

Studies suggest that doxepin has a short-term effect on itch only.

The use of antibacterial agents (e.g., clioquinol) or antibiotics is based on the fact that lesions are often moist and crusted. Secondary staphylococcal infection, as in AD, may aggravate the eczematous process.

Occlusion over a topical corticosteroid has been reported to lead to lesion clearance in previously therapy-resistant patients with discoid lesions due to AD; soaking in water for 20 minutes before treatment application has been recommended for a range of eczemas.

As with other itchy dermatoses, sedating antihistamines may help symptoms; the increase in mast cells in lesions provides the rationale for this approach. However, histamine itself has not been shown to be important.

Second-line therapies

image Phototherapy (broadband or narrowband UVB, 311 nm) E
image Photochemotherapy (psoralen plus UVA, PUVA) E
image Topical immune modulators E
image Cyclosporine E
image Intralesional corticosteroid injection E
image Oral corticosteroids E

Formal trials of these treatments in discoid eczema are lacking and therefore the evidence gradings are weak; however, all are useful in AD or other dermatitis (see gradings in Atopic dermatitis, Chapter 18), and are therefore likely to be effective in discoid eczema. Personal experience is that narrowband UVB or cyclosporine are useful if required.

Third-line therapies

image Azathioprine E
image Methotrexate C
image Mycophenolate mofetil E
image Hypnosis D
image Infliximab E

As for second-line therapies, formal trials of these treatments in discoid eczema are lacking and therefore the evidence gradings are weak; however, all are useful in AD or other dermatitis (see gradings in atopic dermatitis, Chapter 18), and are therefore likely to be effective in discoid eczema.

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