Nummular Dermatitis

Synonyms

Discoid eczema; Nummular eczema

Definition

Dermatitis with sharply-bordered, coin-shaped patches or plaques.

Aetiology & Pathogenesis

Mostly unknown. Microbial colonization, local trauma. Sometimes associated with dry skin and stasis dermatitis. In many patients, particularly children, it is a manifestation of atopic dermatitis.

Signs & Symptoms

Nummular (circular or oval = coin-shaped), exudative patches and plaques, often with crusts. Pruritus, and sometimes excoriations.

Localisation

Sites of predilection: Extremities (lower legs, hands, forearms), trunk occasionally in a symmetrical distribution.

Classification

Different patterns: Discoid eczema of the hands and forearms. Discoid eczema of the limbs and trunk. “Dry” discoid eczema.

Laboratory & other workups

Scales: Direct microscopic examination to exclude fungal infection.

Dermatopathology

Typical histology for dermatitis reflecting acute/subacute nature of lesion, usually few eosinophils (see Atopic Dermatitis).

Course

Chronic, with recurrent flares, may be somewhat resistant to therapy.

Complications

Secondary bacterial infection.

Diagnosis

Clinical features, sometimes histopathological examination and exclusion of fungal infection.

Differential diagnosis

Tinea corporis, psoriasis, irritant and allergic contact dermatitis, cutaneous T-cell lymphoma, impetigo.

Prevention & Therapy

Topical corticosteroids or combinations of corticosteroids with antimicrobials. Acute lesions: Local astringent measures and antiseptics. Disseminated forms: Occasionally oral antibiotics and systemic corticosteroids. Prevention: Emollients and avoidance of irritants.

1.1.2.4 Nummular Dermatitis