Nummular dermatitis

Nummular dermatitis is a chronic inflammatory skin condition characterized by well-demarcated, coin-shaped, pruritic lesions. It typically manifests on the extensor surfaces of the upper and lower extremities and worsens in cold, dry weather. Nummular dermatitis frequently occurs in patients with atopy. The diagnosis is usually clinical. Management is similar to that of atopic dermatitis. The main goal of management is to protect the skin barrier with hydrating skin emollients to prevent and/or treat xerosis. Topical pharmacotherapy is used for mild symptoms, while systemic pharmacotherapy and/or phototherapy may be required if symptoms are severe or persistent.

• Multifactorial
• Primarily an immunologic hypersensitivity reaction (dermatitis) due to xerosis and damage to the epidermal lipid barrier

• 1–5 cm coin-shaped, well-demarcated erythematous plaques
• Pruritus
• Crusting and scaling ^[3]
• Papules and vesicles may be present ^[3]
• Primarily affects the extremities ^[3][4]
• Symptoms worsen during cold, dry weather. ^[4]

Nummular dermatitis often occurs in patients with atopy. ^[4]

• Diagnosis is usually clinical.
• If there is diagnostic uncertainty, consider:
  • KOH test to rule out fungal infections
  • Patch testing to assess for contact dermatitis ^[5]
  • Biopsy ^[6]

• Tinea corporis ^[4]
• Psoriasis
• Contact dermatitis
• Atopic dermatitis
• Urticaria
• Erythema migrans
• Erythema multiforme
• See also “Overview of annular skin lesions.”

The differential diagnoses listed here are not exhaustive.

The management of nummular dermatitis is similar to the management of atopic dermatitis. ^[3][4]

• All patients: nonpharmacological management
  • Maintain skin hydration with emollients.
  • Avoid irritants.
• Mild symptoms
  • Medium or high potency topical corticosteroids (e.g., triamcinolone acetonide 0.1%, fluocinonide 0.05%) ^[7]
  • Topical immunomodulators (e.g., tacrolimus, pimecrolimus)
• Severe or refractory symptoms
  • Refer to dermatology.
  • Treatment options include:
    • Systemic glucocorticoids
    • Systemic immunomodulators ^[8][9]
    • Phototherapy