From the Guidelines
Discoid eczema is a chronic skin condition characterized by round or oval-shaped patches of inflamed, itchy skin, with the most recent guidelines suggesting a complex pathogenesis involving genetic, immunologic, and environmental factors 1.
Key Characteristics
- The condition most commonly affects adults, particularly men, and tends to develop on the limbs, especially the lower legs, though it can appear anywhere on the body.
- The distinctive coin-shaped lesions typically appear red, swollen, and may ooze fluid before becoming dry, crusty, and flaky as they heal.
- Pruritus is a hallmark of the condition, responsible for much of the disease burden borne by patients and their families, as noted in the guidelines for the management of atopic dermatitis 1.
Treatment and Management
- Treatment typically involves topical corticosteroids such as betamethasone valerate 0.1% applied twice daily for 2-4 weeks to reduce inflammation and itching.
- Emollients like petroleum jelly or ceramide-containing moisturizers should be applied liberally at least 2-3 times daily to maintain skin hydration.
- For severe cases, oral antihistamines like cetirizine 10mg daily may help control itching, while infected lesions might require antibiotic treatment.
Prevention and Triggers
- Avoiding triggers is essential - these often include irritants like soaps, detergents, and environmental factors like cold, dry weather.
- The exact cause remains unclear, but it appears to involve a combination of genetic predisposition and environmental factors that disrupt the skin barrier function, leading to inflammation and the characteristic discoid pattern, as discussed in the guidelines for the management of atopic dermatitis in adults with topical therapies 1.
- Unlike other forms of eczema, discoid eczema tends to recur in the same locations and can leave behind darker or lighter patches after healing.
Risk Factors
- A family history of atopy and loss of function mutations in the filaggrin (FLG) gene are consistently and strongly associated with the development of atopic dermatitis, as noted in the guidelines for the management of atopic dermatitis 1.
- Other potential risk factors include elevated birth weights, urban living, and exposure to certain environmental agents, although the evidence is not conclusive.
From the Research
Definition and Characteristics of Discoid Eczema
- Discoid eczema, also known as nummular eczema, is characterized by sharply defined, oval or coin-shaped, erythematous, eczematous plaques 2.
- The size of the lesion varies from 1 to 10cm in diameter, and the lesions are usually multiple and symmetrically distributed 2.
- Sites of predilection include the lower limbs followed by the upper limbs, and the lesions are usually intensely pruritic 2.
Diagnosis and Differential Diagnosis
- The diagnosis is mainly clinical based on the characteristic round to oval erythematous plaques in a patient with diffusely dry skin 2.
- Nummular eczema should be distinguished from other annular lesions, and dermoscopy can reveal additional features that can be valuable for correct diagnosis 2.
- Biopsy or laboratory tests are generally not necessary, but a potassium hydroxide wet-mount examination of skin scrapings should be performed if tinea corporis is suspected 2.
Treatment and Management
- Avoidance of precipitating factors, optimal skin care, and high or ultra-high potency topical corticosteroids are the mainstay of therapy 2.
- Recent patents related to the management of nummular eczema are also discussed, and with proper treatment, nummular eczema can be cleared over a few weeks 2.
- Other treatment options, such as dupilumab, have shown effectiveness in treating nummular eczema phenotype of atopic dermatitis in adults 3.