Nummular Eczema

Nummular Eczema - Coin Lesion Lowdown

• AKA Discoid eczema; chronic, relapsing inflammatory dermatosis.
• Key Feature: Intensely pruritic, coin-shaped (nummular) or oval, erythematous, eczematous plaques.
• Sites: Extensor surfaces of extremities (esp. legs), trunk. Spares face/scalp.
• Epidemiology: Peaks in men (55-65 yrs) & women (15-25 yrs, 55-65 yrs).
• Etiology: Unknown; associations:
  • Dry skin (xerosis), winter months ↑
  • Irritants (soaps, trauma)
  • Staphylococcus aureus colonization/infection
  • Contact allergy (nickel, fragrance)
  • Medications (interferon, retinoids)
  • Atopic diathesis (less common)

⭐ Nummular eczema lesions often start as papules/vesicles that coalesce into sharply demarcated, crusted, or scaling plaques, typically 1-10 cm in diameter. Central clearing may occur, resembling tinea corporis (ringworm).

Nummular Eczema - Itchy Coin Crisis

• Morphology:
  • Sharply demarcated, intensely pruritic, coin-shaped ("nummular") or discoid plaques; typically 1-10 cm.
  • Phases:
    • Acute: Erythematous base with grouped papules/vesicles; may ooze and form crusts.
    • Chronic: Drier, scaly, sometimes lichenified plaques.
• Distribution:
  • Predominantly on extensor surfaces of extremities (especially legs).
  • Trunk and buttocks also common sites.
  • Usually spares the face and scalp.
• Key Factors:
  • More common in older males.
  • Strong association with xerosis (dry skin).
  • Exacerbated by low humidity (winter), irritants, stress.
  • 📌 "COINS": Coin-shaped, Oozing (acute), Itchy, No central clearing, Staph. common.

⭐ Nummular eczema lesions are frequently colonized or secondarily infected with Staphylococcus aureus, which can exacerbate the condition and may require antimicrobial therapy.

Nummular Eczema - Eczema Detective Work

• Diagnosis: Primarily clinical:
  • Characteristic coin-shaped (nummular), well-demarcated plaques.
  • Intensely pruritic; may be vesicular, oozing, or crusted.
  • Typically on extremities (esp. lower legs), trunk; often worse in winter.
• Investigations:
  • KOH microscopy: Negative (essential to exclude tinea).
  • Skin biopsy (if diagnosis uncertain): Shows spongiotic dermatitis, acanthosis.
• Differential Diagnosis Table:

  Condition	Key Differentiator(s)
  Tinea Corporis	Annular, central clearing, active scaly border; +ve KOH
  Psoriasis	Thick silvery scales, Auspitz sign; nail/joint involvement
  Atopic Dermatitis	Strong atopic history (personal/family); flexural lesions
  Impetigo	Golden-yellow ("honey-colored") crusts; less pruritus

⭐ > A key trigger for nummular eczema is skin dryness (xerosis); thus, emollients are crucial in management and prevention, especially in winter.

Nummular Eczema - Soothing Strategies

• Core Principles:
  • Hydration: Liberal emollients (e.g., petrolatum).
  • Gentle Skin Care: Lukewarm baths, soap-free cleansers.
  • Avoid Irritants: Wool, harsh detergents.

⭐ For nummular eczema, potent topical corticosteroids are first-line; failure to respond adequately may indicate secondary infection or need for systemic therapy.

High‑Yield Points - ⚡ Biggest Takeaways

• Presents as coin-shaped (nummular) or discoid plaques; intensely pruritic.
• Commonly on extensor surfaces of extremities, especially legs; more frequent in older males.
• Strong association with xerosis (dry skin), typically worsening in winter.
• Acute lesions: vesicles, oozing, crusting; Chronic: dry, scaly, lichenified plaques.
• Differentiate from tinea corporis (KOH microscopy negative).
• Treatment: Potent topical corticosteroids and liberal use of emollients.
• Often follows a chronic and relapsing course.