What is nummular eczema?

From the Guidelines

Nummular eczema is a chronic inflammatory skin condition characterized by coin-shaped patches that are typically itchy, red, scaly, and well-defined, often appearing on the arms, legs, hands, and torso. The condition is distinct from other forms of eczema due to its unique coin-shaped appearance, which helps in diagnosis and differentiation from other skin conditions. Key characteristics of nummular eczema include:

• Coin-shaped (circular or oval) patches
• Itchy, red, scaly, and well-defined lesions
• Common locations: arms, legs, hands, and torso
• Lesions may ooze, crust over, or become dry and scaly Treatment and management strategies for nummular eczema focus on reducing inflammation, itching, and preventing flare-ups, similar to other forms of eczema, such as atopic dermatitis, where proactive application of topical corticosteroids (TCS) or topical calcineurin inhibitors (TCIs) has been shown to be effective in preventing flares 1. However, the provided evidence primarily discusses atopic dermatitis and its management, with no direct reference to nummular eczema, indicating a need to rely on general principles of eczema management and the distinctive characteristics of nummular eczema for its identification and treatment. Given the lack of specific evidence on nummular eczema in the provided studies, treatment typically involves topical corticosteroids and moisturizing the skin regularly with fragrance-free emollients, applied at least twice daily, especially after bathing while the skin is still damp, along with avoiding triggers like harsh soaps, hot water, wool clothing, and stress to help prevent flare-ups. Antihistamines may also be considered to control itching, although the exact cause of nummular eczema remains unknown, with factors such as dry skin, stress, environmental irritants, and a compromised skin barrier function likely contributing to its development.

From the Research

Definition and Characteristics of Nummular Eczema

• 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.

Clinical 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.
• Moisturizing of the skin and avoidance of identifiable exacerbating factors, such as hot water baths and harsh soaps, may reduce the frequency of recurrence 2.
• Methotrexate can be an effective treatment for severe nummular eczema in children that has failed to respond to conventional topical therapy 3.
• Dupilumab treatment has also shown clinical and molecular efficacy in nummular eczema, supporting the view of nummular eczema as a variant of atopic dermatitis 4.

Clinical Features and Aggravating Factors

• Nummular eczema is an idiopathic inflammatory skin disease that mostly has a chronic and relapsing course 5.
• Many factors are thought to be responsible for this condition, such as atopic dermatitis, dry skin, emotional stress, or seasonal variation 5.
• Emotional stress and drinking alcohol can aggravate the disease, and those who have exacerbation in summer or skin dryness tend to have persisting disease 5.
• The quality of life of patients with nummular eczema can be significantly impaired, especially in younger life, office workers, those with trunk-distributed lesions, and those having extensive lesions 5.