Atopic Eczema

Atopic dermatitis (eczema) is a chronic, relapsing, pruritic (itchy), inflammatory skin condition.

Epidemiology

  • Very common condition with a prevalence as high as 15-20% in children and 2-10% in adults.  It accounts for around 30% of all dermatological consultations in GP.
  • Most present in infancy (85% before 1 year and 95% before 5 years)

Pathophysiology

There are two main theories:

  1. Primary immune dysfunction- there is an imbalance of T-helper cell activity (particularly Th2, but also Th17 acutely and Th1 chronically) causing increased production of Th2 cytokines e.g. IL4, IL5, IL13, which cause increased IgE production.
  2. Epidermal barrier dysfunction- antigen entry is easier and promotes a hypersensitive immune system.  AD is often associated with ichthyosis/xerosis (dry skin).  A key gene found to be important to skin barrier function and in the development of both conditions is that of filaggrin.  

Presentation

  • Itch is the predominant symptom (no itch- probably not eczema)
    • Accompanied by a rash (see below)
    • Episodic in nature, usually starting in childhood/infancy
    • A family history is common; ask also about a family history of other atopic conditions e.g. rhinitis (hay fever) and asthma
    • Ask about a personal medical history of atopic conditions/allergies
  • The rash is usually erythematous, but may also have other features and different distributions depending on the age/stage of AD.  Acute exacerbations may appear as a vesicular rash, increased scale/crusting or just more marked redness.
    • Infancy:- face, scalp and extensor surfaces are commonly affected (nappy area usually spared and NB- the flexural surfaces may be affected briefly first). The rash is also usually quite erythematous but they can scale and skin may be dry all over the body.
    • Children:- flexural surfaces are most commonly affected.  With long-standing eczema, lichenification is common (thickening of the skin caused by prolonged rubbing/scratching).  Again, dry skin is found all over the body.
    • Adults:- as well as flexural surfaces, the hands are also a common site with exposure to irritants.
    • NB in patients of Asian, Black-Caribbean or Black-African ethnicity, atopic eczema can more commonly affect the extensor surfaces, and discoid/follicular patterns of eczema may occur more often

Diagnostic Criteria

  • Itchy skin in the last 12 months + 3 or more of
    • Involvement of the skin creases
    • History of asthma or hay fever (or that of a first degree relative if the child is <4)
    • Dry skin
    • Onset <2 years (unless currently <4)
    • Visible flexural eczema (if under 4, also facial, scalp and extensors)
  • Assessing severity
    • Clear: normal skin, no evidence of active eczema
    • Mild: areas of dry and erythematous skin with infrequent itching
    • Moderate: areas of dry, red skin with frequent itching (+/- excoriations and localised skin thickening)
    • Severe: widespread areas of dry, red skin with incessant itching (+/- excoriations, lichenification, bleeding, oozing, cracking, pigment changes)
    • NB Also important to assess the impact on the quality of life.

Triggers

  • Soaps/detergents (shampoo, shower gel, washing-up liquid etc)
  • Physical factors (e.g. temperature, humidity)
  • Diet (more common in children/infants e.g. milk and it is important to ask about other symptoms e.g. nausea/vomiting, oedema, wheeze, and in infants, weight/feeding etc)
  • Inhalents (e.g. dust mites, pollens, pet dander)
  • Hormones (not uncommon to have a flare pre-menstrual stage and pregnancy)
  • Stress

Investigations

Most cases are a clinical diagnosis but most will also require some form of allergy testing (either RAST or patch testing).

Management

The management of patients with atopic eczema is comprised of several things:

  1. Advice of itching/scratching (avoidance- rub instead/nail length)
  2. Avoidance of triggers (NB if dust mite is the presumed cause, it is not advisable to introduce reduction measures as these are costly, time-consuming and of limited effect.
  3. Emolients should be prescribed (with directions for use) and applied regularly and liberally.  Oil based emollients are better for acute flare-ups e.g. epaderm, however, these can be very greasy so patients usually prefer water-based emollients (e.g. diprobase) for everyday use.  It is also often useful to arrange the use of soap/showering substitutes
  4. Topical steroids are used for symptomatic relief of the inflammation and itch:
    1. Mild AD can usually be managed with a mild potency steroid e.g. hydrocortisone
    2. Moderate AD may require a moderate steroid (e.g. eumovate) at least initially.  NB It is recommended that facial eczema only be treated with a mild steroid (however, sparing use- max 5 days- of a moderate steroid may be used initially)
    3. Severe AD may require a potent steroid (e.g. betnovate).  Rarely, oral steroid (30mg prednisolone) may be used (usually restricted to extensive/severe eczema causing significant psychosocial distress).
      1. If this is not controlling symptoms, consider trying a super potent steroid e.g. dermovate.
      2. Once the acute flare has remitted, use a step down approach to topical steroid use
      3. If >2 flares/month persist, consider admission for intensive treatment.
  5. A non-drowsy antihistamine can also be used (e.g. certirizine).
  6. Topical calcineurin inhibitors (tacrolimus) are a second line option.  Common side effects include burning and redness.  It should not be used in pregnancy, immunosuppressed patients, in skin cancer patients
  7. PUVA may be used in severe eczema that is proving refractory to treatment

Special cases

  • Infected eczema
    • Features of infected eczema include crusting, weeping, pustulation and/or surrounding cellulitis/erythema of normal skin
    • It may also present as a sudden worsening of the condition with a resilience to regular treatment.
    • Fever/malaise may also be a feature
      • Swabbing is not usually required unless there is a suspicion that a resistant organism is involved or that the infection is severe enough to warrant oral antibiotics
        • If severe/extensive, flucloxacillin should be used.  If localised, then a topical antibiotic may be adequate (usually combined with a topical steroid e.g. Fucidin H (Hydrocortisone + Fusidic acid) or Fusibet (Betnovate + Fusidic acid))
  • Eczema Herpeticum (emergency)
    • Suggested by a rapidly worsening and painful eczema.  Often presenting with clustered and umbilicated (central punched out core) blisters that may be oedematous, crusted or haemorrhagic.
    • It can also be associated with fever, lethargy and distress.
    • It is caused by herpes simplex infection on top of eczematous skin.
    • If at all suspected, a viral swab should be taken and oral antivirals started.
    • Danger of fluid loss from the skin (may require fluid replacement and U&E monitoring)
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