A 50-year-old man presented with very itchy, round patches on both legs.
The patches were coin-shaped, well-defined and symmetrical. There was some crusting and vesicles on the lesions. The man had no history of atopy or other skin disease. What is the diagnosis and management? What is the differential diagnosis?
Diagnosis and management
The diagnosis is discoid eczema, also known as nummular eczema due to its coin-shaped lesions.
Discoid eczema is a common recurrent condition of unknown aetiology.
It is more common in middle-aged men but can appear at any age. Sometimes it clears spontaneously, but usually requires topical steroids. In case of bacterial secondary infection, topical or oral antibiotics should be considered.
Possible differential diagnoses:
- Allergic contact dermatitis.
- Tinea corporis.
- Pityriasis rosea.
- Plaque psoriasis.
- Guttate psoriasis.
Allergic contact dermatitis
- Delayed hypersensitivity reaction to an external allergen.
- Common allergens are nickel, colophony, rubber additives, hair dyes or topical medicines.
- It can be occupational; for example, nurses and hairdressers.
- Presents as red, itchy patches.
- Patch testing helps identify the allergen.
Contributed by Dr Paula Hensler, clinical editor, GP, and editor, MIMS Dermatology.