Eczema

last authored:
last reviewed:

 

 

 

Introduction

Eczema is a clinical term describing many pathogenically different conditions. The Greek word eczema means "to boil over". All are characterized by red, papilovesicular, oozing, and crusted lesions which develop over time into raised, scaling plaques. Small and larger blisters (vesicles and bullae) may be present.

Over time, vesicles can become progressively scaly (hyperkeratotic) as the epidermis thickens (acanthosis).

 

 

The Case of...

a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.

return to top

 

 

 

Causes and Risk Factors

Local irritants more often contribute than foods - wool clothing, sand/dirt, saliva, heat/cold, dry air

return to top

 

 

 

Pathophysiology

Edema occurs within the intercellular spaces of the epidermis, primarily the stratum spinosum. Mechanical shearing of desmosomes and cell membranes by fluid accumulation results in intraepidermal vesicles.

 

Epidermal antigens are taken up by Langerhans cells, which then migrate to draining lymph nodes. Antigens are processed and presented to naitve CD4+ T cells, which are activated and develop into effector and memory T cells.

On re-exposure, these T cells migrate to affected skin sites, releasing cytokines and other factors recruiting inflammatory cells.

Early cytokine release causes venule endothelial activation, promoting memory T cell adhesion and extravasation. Expression of an array of lymphokines recruits large numbers of inflammatory cells within 24 hours. This accounts for initial erythema and pruritus acompanying cutaneous delayed hypersensitivity.

 

Chronic exposure to UV damages epidermal Langerhans cells, required for the development of contact hypersensitivity. Neuropeptides also appear to affect Langerhans cell function, suggesting implications for neural roles in the development and severity of certain dermatidites.

 

Dryness, itch, inflammation, infection

 

endogenous

• atopic dermatitis (usually what people refer to as eczema)
  • affected by 10-17%
  • associated with allergy, hay fever
  • aka flexure derm b/c it is often in elbows, knees, wrist
  • can be acute, subacute, or chronic
  • characterized by marked puritus - scratching can lead to lichenificatrion
  • caused by aberrant T cells
  • excessive Th2 cell resonse to antigens, langerhans cells involved as well

     

• seborrheic dermatitis - dandruff
  • thick, adherent, waxy scales
  • scalp (cradle cap), middle of forehead, eyebrows, centre of chest, ears, body folds, around umbilicus
• nummular dermatitis - coin-shaped
  • round (coin-shaped)
  • solid, unlike ringworm
• stasis dermatitis -
• dyshidrosiform dermatitis - though has nothing to do with sweating
  • usually on palms and soles
  • can be intensely itchy
  • small collections of edematous fluids under the skin

exogenous (contact dermatitis)

• irritant
• allergic
  • type I - rapid (IgE),
  • type IV slower
• photoeczematous

 

unclassified

• lichen simplex chronicus
  • occurs with veins under pressure (varicose veins) with skin leaking and edematous outflow

     

• juvenile plantar dermatitis
• asteatotic dermatitis

 

return to top

 

 

 

Signs and Symptoms

return to top

 

 

 

Investigations

return to top

 

 

 

Differential Diagnosis

 

return to top

 

 

 

Treatments

take a really good history; ask all about what products they use.

Acute:

• remove precipitating factors and protect the affected area.
• avoid irritants and use moisturizers
• "soak and seal"; avoiding soap except in the smelly areas.
• itch: hydroxyzine
• Treat any secondary infection with topical antibiotic such as fucidin. Consider cephalexin
• apply soaks or compress with saline or Burrow's solution (1:40) (aluminum based, antibiotics) to dry skin
• use corticosteroid cream, tapered to a moisturizer
  • hydrocortisone on face and genitals
  • betamethasone for body
  • tacrolimus (Protopic) and picrolimus (Elidel)

  no thinning of the skin with tacrolimus/pimocrolimus

chronic:

• remove precipitating factors and protect affected area
• treat secondary infection
• apply corticosteroid cream, tapered to a moisturizer

return to top

 

 

 

Consequences and Course

 

return to top

 

 

 

Resources and References

 

return to top

 

 

Topic Development

authors:

reviewers:

return to top