Discoid Eczema (Nummular Dermatitis)

Introduction | Aetiology and Risk Factors | Clinical Presentation | Diagnosis | Management and Treatment | Prevention | When to Refer | References

Introduction

Discoid eczema, also known as nummular dermatitis, is a chronic skin condition characterised by coin-shaped, itchy, and inflamed patches on the skin. These lesions often appear on the limbs, but they can occur anywhere on the body. The exact cause of discoid eczema is not fully understood, but it is thought to be associated with dry skin, skin injuries, or underlying skin conditions such as atopic dermatitis. The condition can be recurrent and is often difficult to manage, requiring a combination of lifestyle changes and medical treatments.

Aetiology and Risk Factors

Discoid eczema is multifactorial, with several contributing factors and triggers:

• Dry Skin: Dry skin is a significant risk factor as it can lead to skin barrier dysfunction, making the skin more susceptible to irritation and inflammation.
• Skin Injuries: Trauma to the skin, such as cuts, abrasions, insect bites, or burns, can trigger the development of discoid eczema in susceptible individuals.
• Atopic Dermatitis: Individuals with a history of atopic dermatitis are at higher risk of developing discoid eczema.
• Environmental Factors: Cold weather, low humidity, and exposure to irritants like soaps, detergents, and chemicals can exacerbate the condition.
• Infections: Bacterial infections, particularly with Staphylococcus aureus, can complicate discoid eczema, leading to worsening symptoms.
• Stress: Psychological stress can be a contributing factor, as it is known to exacerbate many chronic skin conditions, including discoid eczema.
• Age and Gender: Discoid eczema can affect people of all ages, but it is more common in middle-aged and older adults. It occurs more frequently in men.

Clinical Presentation

The presentation of discoid eczema is distinctive, with the following features:

• Coin-shaped Lesions: The hallmark of discoid eczema is the appearance of round or oval, coin-shaped patches of eczema. These lesions are usually red, scaly, and well-demarcated.
• Itching: Intense itching is a common symptom and can be severe, often leading to scratching, which exacerbates the condition.
• Inflammation: The affected areas may be inflamed, with the skin appearing swollen, warm, and tender to the touch.
• Crusting and Oozing: In more severe cases, the lesions may ooze clear fluid, leading to crusting and increased risk of secondary infection.
• Location: Lesions commonly occur on the arms, legs, hands, and torso, but they can appear anywhere on the body. The lesions often occur in clusters.
• Chronic and Recurrent: Discoid eczema tends to be chronic with periods of remission and flare-ups, often triggered by environmental factors or stress.

Diagnosis

The diagnosis of discoid eczema is primarily clinical, based on the characteristic appearance of the lesions and patient history:

• History: Take a detailed history, including the onset of symptoms, any known triggers, history of atopic dermatitis or other skin conditions, and any recent skin injuries or infections.
• Physical Examination: Examine the skin for the distinctive coin-shaped lesions and assess for signs of secondary infection, such as crusting, oozing, or pus formation.
• Differential Diagnosis: Consider other conditions that may present similarly, such as psoriasis, tinea corporis (ringworm), contact dermatitis, or pityriasis rosea.
• Skin Swab: If secondary infection is suspected, a swab for bacterial culture may be taken to identify the causative organism and guide antibiotic therapy.
• Biopsy: In atypical cases or when the diagnosis is uncertain, a skin biopsy may be performed to rule out other conditions such as cutaneous lymphoma or other dermatoses.

Management and Treatment

Management of discoid eczema involves reducing inflammation, relieving itching, and preventing recurrence through a combination of topical treatments and lifestyle modifications:

1. Topical Treatments

• Topical Corticosteroids: These are the mainstay of treatment for reducing inflammation and itching. The choice of potency depends on the severity and location of the lesions:
  • Hydrocortisone 1%: A mild steroid suitable for sensitive areas or for use in children.
  • Betamethasone valerate 0.1%: A moderate to potent steroid used for more severe lesions on thicker skin areas.
• Topical Calcineurin Inhibitors: Tacrolimus or pimecrolimus may be used as steroid-sparing agents, particularly for long-term management or in sensitive areas like the face.
• Emollients: Regular use of emollients is essential to restore the skin barrier, reduce dryness, and prevent flare-ups. Recommend fragrance-free, hypoallergenic emollients.
• Antibiotic Creams: If secondary bacterial infection is present, topical antibiotics like fusidic acid or mupirocin may be prescribed.

2. Oral Treatments

• Oral Antibiotics: In cases of secondary bacterial infection, oral antibiotics such as flucloxacillin or erythromycin may be required.
• Oral Antihistamines: These can help control itching, especially if it interferes with sleep. Non-sedating antihistamines like cetirizine or loratadine are preferred during the day.
• Oral Corticosteroids: In severe or widespread cases, a short course of oral corticosteroids may be necessary to control the inflammation.

3. Lifestyle and Supportive Care

• Avoid Triggers: Identify and avoid potential triggers such as harsh soaps, detergents, and irritants. Advise the use of mild, fragrance-free products for skin and laundry.
• Moisturising Routine: Encourage regular use of emollients, especially after bathing, to maintain skin hydration and integrity.
• Stress Management: Psychological stress can exacerbate eczema. Techniques such as mindfulness, relaxation exercises, or counselling may be beneficial.
• Wet Wrap Therapy: In severe cases, wet wrap therapy can be used to enhance the absorption of topical treatments and provide relief from itching.

Prevention

Preventive measures are key to managing discoid eczema, particularly in preventing flare-ups:

• Regular Moisturising: Consistent use of emollients helps maintain the skin barrier and prevent dryness, which can trigger flare-ups.
• Gentle Skincare: Advise patients to use gentle, fragrance-free products and to avoid hot water, which can further dry out the skin.
• Protective Measures: In occupations or situations where the skin is exposed to irritants, recommend protective clothing or gloves.

When to Refer

Referral to a dermatologist may be necessary in the following situations:

• Severe or Refractory Cases: If discoid eczema does not respond to standard treatments or if the condition is severe, referral to a specialist is advised.
• Uncertain Diagnosis: If the diagnosis is unclear or if the presentation is atypical, a dermatologist's input may be required to rule out other conditions.
• Need for Specialist Treatments: In cases where more advanced therapies such as phototherapy or systemic immunosuppressants are considered, specialist referral is appropriate.

References

1. British Association of Dermatologists (2024) Guidelines for the Management of Discoid Eczema. Available at: https://www.bad.org.uk (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (2024) Discoid Eczema: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng105 (Accessed: 26 August 2024).
3. British National Formulary (2024) Topical and Oral Treatments for Dermatological Conditions. Available at: https://bnf.nice.org.uk/ (Accessed: 26 August 2024).