discoid eczema

Discoid eczema also known as nummular dermatitis, is the long term inflammation of the skin presented with coin shaped patches, itching, swelling and cracked skin. The condition can last from weeks to years without treatmen. It is a localised (specific area) version of atopic (caused by allergies) inflammation fo the skin.

Epidemiology

According to Patient UK, approx 2 per 1000 people are affected my discoid eczema
More common in men than women
Peak incidence in ages 50-65 years, second most likely in 15-25 years [1]
It is uncommon in children
More commonly found in nonwhite children [2]

Source: Waikato District Health Board; DermNetNZ

Discoid eczema
Hyperpigmentation shown on skin of colour

Pathophysiology [3]
- Medical Student
  - Discoid eczema's pathophysiology is often associated with xerosis (dry skin).
  - The condition likely results from a combination of epidermal lipid barrier dysfunction and an immunologic response.
  - Dry skin leads to a compromised lipid barrier, allowing allergens and bacteria to penetrate the skin and trigger an allergic or irritant immune response.
  - Impaired cutaneous barrier in discoid eczema can increase susceptibility to allergic contact dermatitis from materials like metals, soaps, and chemicals.
  - Increased mast cells have been observed in lesions of discoid dermatitis, suggesting their potential role in the disease process.
  - Neurogenic factors, involving mast cells and sensory nerves, may contribute to inflammation and pruritus in discoid eczema.
  - Connections between mast cells and nerves, as well as certain neuropeptides, are increased in discoid eczema compared to normal skin.
  - Mast cells in discoid eczema may have decreased chymase activity, leading to reduced suppression of inflammation.
  - Colonisation of the skin with Staphylococcus aureus has been observed in discoid eczema patients and their close contacts, but its exact significance in the disease remains uncertain.
- Patients
  - Discoid eczema's pathophysiology is often associated with dry skin.
  - The condition likely results from a combination of a fault with the skin barrier and response from the immune system.
  - Dry skin creates an environment on the skin where allergens and bacteria can penetrate the skin easier and trigger an allergic or irritant immune response.
  - The impaired skin barrier in this condition can increase susceptibility to allergic contact dermatitis (inflammation of the skin when in contact with certain objects) from materials like metals, soaps, and chemicals.
  - There is also an increase in the cells involved in the allergic response, called mast cells, which has been seen in discoid eczema.
  - Nerves and cells, including the mast cells and sensory nerves, may contribute to inflammation and itchiness in discoid eczema.
  - Connections between mast cells and nerves, as well as certain transmitters of signals in the body are increased in discoid eczema compared to normal skin.
  - Mast cells in discoid eczema may have decreased chymase (a substance present when mast cells are activated) activity, leading to a drop in the suppression of inflammation.
  - Presence and growth of the skin with Staphylococcus aureus has been observed in discoid eczema patients and their close contacts, but its exact significance in the disease remains uncertain.

Source: Primary Care Dermatology Society

Discoid eczema
Redness in patch-shaped distributions on the lower legs

Source: Primary Care Dermatology Society

Discoid eczema
Circular patches with hyperpigmentation (darker spots)

Causes
- Staphlyococcus aureus infection
- Impetigo or wound infections [4]
- History or presence of dry skin
- Exposure to irritants such as cosmetics and toiletries
- History of atopic eczema
- Triggered by minor injuries such as bites or burns
- Dry environments and cold climates [5]
- Stress can aid its development
- Varicose veins (weak vein walls that are swollen and enlarged) [6]

Risk factors [7]
- Patients with a history of atopic dermatitis (AD)
- A blood relative with hay fever, AD or asthma
- History or presenting with varicose veins or stasis dermatitis
- History of contact dermatitis

Presentations [8]
- Redness (erythematous)
- Scaly
- Itchiness (pruritus)
- Coin shaped and well defined borders
- Affects trunk, buttocks and extensor regions such as elbows

Source: DermNetNZ.org

Discoid eczema
Circular borders with flaky skin and redness with a pink centre

Source: DermNetNZ.org

Discoid eczema
Presentation on the trunk in a cluster distribution

Investigations [9]

Skin biopsy- sample of skin is taken for investigation under microscope
Patch test- Different potentially allergy inducing substances are placed on the skin and taped in place. The patches are typically placed on the skin, left on for 2 days and then removed to check for a reaction to certain substances.
Skin scrapings and swabs can check for potential fungal and bacterial infections respectively

Differential diagnosis [4]
- Psoriasis- Inflammatory skin condition with redness, plaques and itchiness
- Tinea corporis (ringworm)- Fungal infection that causes circular rashes
- Contact dermatitis- Inflammatory condition with dry skin causes redness and itchiness
- Lichen simplex- Plaques that are associated with discoid eczema
- Statis dermatitis- Poor lack of blood supply in the lower legs

Source: DermNetNZ.org

Discoid eczema
Well defined borders in discoid eczema on the leg

Source: Waikato District Health Board; DermNetNZ

Discoid eczema
Hyperpigmentation in skin of colour

Management [7]

Medical Students
- Lifestyle changes:
  - Remain hydrated:
    - Take a daily bath or shower up to 20 minutes in lukewarm water.
    - Add bath oil (recommended by your doctor) to your bath
    - Apply moisturiser to damp skin within minutes of bathing.
    - Use a humidifier in your bedroom to keep the room cool and moist.
    - Consider hypoallergenic, fragrance-free moisturizing creams or ointments instead of lotions for better water retention.
  - Avoid irritating your sensitive skin:
    - Use a mild, non-drying cleanser only on necessary areas.
    - Opt for loose-fitting cotton clothing.
    - Stay away from heat sources like fireplaces and heaters.
    - Use a humidifier in your bedroom for a cool, moist environment.
- Medications and testing:
  - Treat the spots and patches on your skin:
    - Medication or light treatments prescribed by your dermatologist, such as;
    - Corticosteroid ointment
    - Tacrolimus ointment
    - Pimecrolimus cream
    - Tar cream
      - This can help reduce inflammation and itching.
    - Apply medication to damp skin after bathing for better results.
      - More severe cases may require medicated dressings, oral corticosteroids, or phototherapy treatments.
  - Treat infections:
    - Your doctor may prescribe medications applied to the skin or taken orally to clear infections.
  - Consider patch testing:
    - If discoid eczema persists, patch testing may be recommended to identify possible triggering allergies.
    - Studies have shown that allergies are often a reason for persistent nummular eczema, and treating the allergy can lead to improvement.

Patients
- Lifestyle changes:

Remain hydrated:
- Take a daily bath or shower up to 20 minutes in lukewarm water.
- Add bath oil (recommended by your doctor) to your bath
- Apply moisturiser to damp skin within minutes of bathing.
- Use a humidifier in your bedroom to keep the room cool and moist.
- Consider hypoallergenic, fragrance-free moisturizing creams or ointments instead of lotions for better water retention.
Avoid irritating your sensitive skin:
- Use a mild, non-drying cleanser only on necessary areas.
- Opt for loose-fitting cotton clothing.
- Stay away from heat sources like fireplaces and heaters.
- Use a humidifier in your bedroom for a cool, moist environment.

Medications and testing:
- Treat the spots and patches on your skin:
  - Medication or light treatments prescribed by your dermatologist, such as;
  - Corticosteroid ointment
  - Tacrolimus ointment
  - Pimecrolimus cream
  - Tar cream
    - This can help reduce inflammation and itching.
  - Apply medication to damp skin after bathing for better results.
    - More severe cases may require medicated dressings, oral corticosteroids, or phototherapy treatments.
- Treat infections:
  - Your doctor may prescribe medications applied to the skin or taken orally to clear infections.
- Consider patch testing:
  - If discoid eczema persists, patch testing may be recommended to identify possible triggering allergies.
  - Studies have shown that allergies are often a reason for persistent nummular eczema, and treating the allergy can lead to improvement.

Source: Waikato District Health Board: DermNetNZ

Discoid eczema
Patches of hyperpigmentation on the lower leg

Source: Waikato District Health Board: DermNetNZ

Discoid eczema
Scaling over discoid eczema

Complications [1]
- Bacterial infections at the site of eczema
- Permanent brown (or purple, dark brown in darker skin) discolouration

Myths

There is only one type of eczema
Itchy skin isn’t a red flag
It will self resolve
Treatment will cure/eradicate eczema
Lifestyle changes won’t singularly help eczema
Atopic dermatitis is contagious
Family history will mean future generations will experience it
Atopic dermatitis is caused by stress [10,11]

Questions you may want to ask your doctor
- What can I do to manage my symptoms?
- Are there any products that can make my eczema worse?
- Are there ways I can treat my skin to reduce my chances of another flare up?
- What should I do if the medication doesn’t work?
- When should I apply/use my medication?
- How can I find out what is causing my condition?
- How can I protect myself against allergens/ irritants?
- What can I do to prevent complications of discoid dermatitis?
Support
- The British Association of Dermatologists
- The National Eczema Society
- Eczema Care Online Association