Nummular Eczema: Diagnosis and Management

Nummular (discoid) eczema presents as coin-shaped, well-demarcated, pruritic plaques. It's a distinct eczema variant often triggered by skin barrier disruption.

Clinical Features

• Round or oval plaques, 1–10 cm, erythematous (violaceous in dark skin), scaly, crusted, sometimes exudative.
• Intense pruritus; burning or stinging.
• Common sites: Legs (especially pretibial), dorsal hands, forearms, trunk.
• Often asymmetric; may coalesce.
• More common in men 50–65; also young adults (atopic background).

Triggers

• Xerosis (dry skin) — major factor.
• Contact irritants or allergens (metals, fragrances, preservatives).
• Skin trauma (scratches, insect bites).
• Cold, dry weather; low humidity.
• Stress, poor sleep.
• Medications (rare: IFN-γ, TNF inhibitors, statins).
• Staphylococcal colonization (superinfection).

Diagnosis

• Clinical (classic morphology plus history).
• KOH prep or culture if exudative or crusted (rule out tinea, bacterial superinfection).
• Patch testing if contact allergy suspected.
• Biopsy rarely needed (spongiotic dermatitis; excludes lymphoma, mycosis fungoides).

Treatment

Topical (First-Line)

• Mid- to high-potency corticosteroids (triamcinolone 0.1%, mometasone, clobetasol for thick plaques) — 2–4 weeks, then taper.
• Calcineurin inhibitors (tacrolimus 0.1%, pimecrolimus) for maintenance and sensitive areas.
• Crisaborole, ruxolitinib (newer non-steroidal).
• Occlusion (plastic wrap) overnight for thick plaques.

Systemic (Severe/Refractory)

• Narrowband UVB phototherapy (excellent for widespread).
• Short-course oral prednisone (flare bridge).
• Immunosuppressants: Methotrexate, cyclosporine, azathioprine, mycophenolate.
• Dupilumab (IL-4/13 inhibitor) — highly effective for nummular phenotype.
• JAK inhibitors (upadacitinib, abrocitinib) — emerging.

Adjunctive

• Aggressive moisturization (ceramide creams, ointments) — lifelong.
• Antihistamines (sedating at night for sleep).
• Antibiotics if secondary infection (cephalexin, doxycycline).
• Wet wrap therapy (see separate article).

Prevention

• Daily moisturizing (especially legs and arms).
• Humidifier in winter.
• Avoid known irritants and allergens.
• Gentle skin care (lukewarm water, fragrance-free).
• Stress management.

Nummular eczema is chronic-relapsing. Long-term maintenance focuses on barrier integrity and trigger avoidance.