Nummular Dermatitis | Visual Dermatology Atlas

Illustration of the main clinical features of nummular eczema, including well-demarcated round, “coin-shaped” plaques, sometimes with more prominent borders, associated with intense pruritus. Lesions commonly affect the legs, and flares may be more promin

General info +

AKA: Discoid eczema / Nummular dermatitis

• Inflammatory dermatitis characterized by round or oval, “coin-shaped” eczematous plaques with prominent pruritus.
• Acute lesions may be papulovesicular, oozing, and crusted.
• More common in adults, particularly middle-aged and older adults.
• Often worsens during cold, dry seasons (fall and winter).
• Xerosis (dry skin) is common.
• An atopic background may be present but is not required.
• May follow a chronic or relapsing course.

Symptoms / presentation +

• Development of round, intensely pruritic plaques.
• Pruritus may be severe and lead to secondary excoriations.
• Flares are often associated with dry skin, particularly during winter.
• Lesions may initially be oozing and subsequently become scaly and thickened.

Clinical exam +

• Well-demarcated, round or oval erythematous plaques.
• Characteristic “coin-shaped” appearance.
• Papules and small vesicles may coalesce into plaques.
• Borders may appear more prominent than the center.
• Acute phase: oozing ± crusting.
• Chronic phase: scaling, excoriations ± lichenification.
• Yellow crusting, pustules, or purulent drainage may indicate secondary bacterial infection.

Distribution +

• Legs +++, particularly the lower legs.
• Arms and forearms.
• Trunk.
• Lesions may be multiple and bilateral.
• Face and scalp are generally spared.

Dermoscopy +

• Erythematous background.
• White to yellow scales.
• Yellowish serous crusts may be present in exudative lesions.
• Dotted vessels may be present, usually with an irregular distribution.
• Dermoscopy may help differentiate nummular eczema from psoriasis and dermatophytosis.

Diagnostic +

• Primarily a clinical diagnosis.
• KOH preparation ± fungal culture if dermatophytosis is suspected.
• Patch testing if allergic contact dermatitis is suspected or disease is persistent/recurrent.
• Bacterial culture if secondary infection is suspected.
• Skin biopsy is rarely required but may be considered for atypical or persistent lesions.

Differential diagnosis +

• Tinea corporis.
• Allergic contact dermatitis.
• Irritant contact dermatitis.
• Plaque psoriasis.
• Atopic dermatitis.
• Impetigo.
• Mycosis fungoides, particularly with atypical or persistent plaques.
• Hailey-Hailey disease, less typically.

Treatment plan +

• Frequent and generous use of emollients, particularly after bathing.
• Minimize hot showers, harsh soaps, frequent washing, and other skin irritants.
• Topical corticosteroids of appropriate potency are first-line for active lesions.
• Clobetasol propionate 0.05% once or twice daily for 7–14 days may be used for thick plaques on the trunk or extremities.
• Betamethasone dipropionate 0.05% once or twice daily for 1–2 weeks, depending on formulation and location.
• Wet compresses may be useful for acute, exudative lesions.
• Antibiotics only when clinical bacterial infection is present.
• Extensive or refractory disease: narrowband UVB phototherapy or specialist-directed systemic therapy may be considered.
• Identify and avoid relevant irritants, triggers, and contact allergens.

References +

DermNet — Discoid eczema (nummular dermatitis)
American Academy of Dermatology (AAD) — Nummular eczema
UpToDate — Nummular dermatitis
Bolognia JL, Schaffer JV, Cerroni L. Dermatology. Elsevier.