Symptoms and Causes of Nummular Eczema
Nummular eczema is characterized by sharply defined, coin-shaped, erythematous, intensely pruritic plaques that typically range from 1-10cm in diameter, most commonly affecting the lower and upper extremities, and is often associated with skin dryness, emotional stress, and potential contact allergies. 1
Clinical Features
- Nummular eczema presents with multiple, symmetrically distributed, round or oval-shaped eczematous plaques 1
- Lesions predominantly affect the lower extremities (90%) followed by upper limbs, with trunk involvement less common 2
- Intense pruritus (itching) is a hallmark symptom that significantly impacts quality of life 2, 1
- Co-existing skin dryness is present in approximately two-thirds of patients 2
- The condition typically follows a chronic, relapsing course with periods of exacerbation and remission 1
- Peak incidence occurs in the third decade of life, with women comprising about two-thirds of patients 2, 3
Causes and Aggravating Factors
- The exact etiopathogenesis remains unclear, but several contributing factors have been identified 1, 4
- Recent research suggests nummular eczema may be a variant of atopic dermatitis with overlapping type 2 and type 3 immune signatures 4
- Contact allergy is common, with 32.5% of patients showing positive patch test reactions to one or more allergens 3
- Common allergens include nickel sulfate (10.2%), potassium dichromate (7.3%), and cobalt chloride (6.1%) 3
- Approximately 14% of patients have a history of atopic dermatitis, and about half have a history of atopy or contact dermatitis 2
- Emotional stress and alcohol consumption can trigger or worsen symptoms 2
- Seasonal variations affect disease activity, with some patients experiencing exacerbations during summer months 2
- Dry skin is both a predisposing factor and an aggravating condition 2, 1
- Dental infections have been identified as potential aggravating factors in treatment-resistant cases 5
- Soaps and detergents can remove natural skin lipids, worsening already dry skin 6
Diagnostic Features
- Diagnosis is primarily clinical, based on characteristic round to oval erythematous plaques in patients with diffusely dry skin 1
- Dermoscopy can reveal additional features valuable for correct diagnosis 1
- Histopathology shows features of both atopic dermatitis (impaired epidermal barrier, spongiosis, eosinophil infiltration) and some aspects of psoriasis (increased epidermal thickness, neutrophilic infiltration) 4
- Patch testing should be considered in patients with chronic, recalcitrant nummular eczema to identify potential contact allergens 1, 3
- Potassium hydroxide wet-mount examination of skin scrapings should be performed if tinea corporis is suspected 1
Common Pitfalls in Diagnosis
- Nummular eczema can mimic other annular lesions, leading to misdiagnosis 1
- Failure to consider contact allergies may result in persistent symptoms despite treatment 3
- Overlooking potential focal infections, such as dental infections, in treatment-resistant cases 5
- Not recognizing the condition as a potential variant of atopic dermatitis, which may influence treatment approaches 4
Management Considerations
- Avoidance of identified triggers and optimal skin care are cornerstones of management 1
- High or ultra-high potency topical corticosteroids are the mainstay of therapy for acute flares 1
- Regular use of emollients helps maintain skin hydration and may reduce recurrence frequency 1, 7
- Patients should avoid hot water baths and harsh soaps that can exacerbate skin dryness 1
- Recent research suggests dupilumab (anti-IL-4Rα) may be effective, supporting the view of nummular eczema as a variant of atopic dermatitis 4