Lec 4: Eczema Flashcards
Eczema Causes
intense itchiness > scratching.
Dermatitis
skin inflammation (broader term than eczema)
Eczema histology
Acute
Chronic
Acute Stage eczema
- Epidermis oedema > spongiosis.
- Intra-epidermal vesicles
- Vesicles coalesce into larger blisters or rupture.
- Plasma weeping.
- Crusting
Chronic Stage Eczema
- Less spongiosis & vesication.
- Prickle (acanthosis) & horny layer (hyperkeratosis & parakeratosis) thickening.
- Variable degree of vasodilatation and infiltration with lymphocytes.
- Scales, fissures, lichenification appear.
Eczema Pathogenesis
Hallmark > inflammation & activated keratinocytes
Eczema TSAD
T: plaques.
S: red, scaly, ill-defined.
A: not specific.
D: asymmetrical, on wrists & flexures.
Eczema Complications
- 2ry bacterial infection > recurrent impetigo.
- Itchy sleepless child > wreck family life.
- Can interfere with work, sporting activities, sex lives, and job.
Eczema Investigations
Biopsy > confirmatory.
Irritant Contact Dermatitis (ICD) epidemiology
80% of dermatitis cases
Common in children.
ICD Etiology
- Brief contact with strong irritants.
- Prolonged contact with weak irritants.
- People with very dry skin.
- Past or present atopic dermatitis increase the risk.
ICD Distribution
Hands & forearms.
ICD Common irritants:
Water, detergents, chemicals, solvents, cutting oil & abrasive dusts.
ICD Course
- The need to continue at work, often stops the skin regaining its normal barrier function.
- Even under ideal circumstances, it may take several months.
- Probably reversible in the early stages.
- In most cases, it becomes chronic.
ICD Complications
May lead to loss of work.
ICD Differential Diagnosis:
Allergic contact dermatitis.
Atopic eczema.
Is patch test helpful in ICD?
No :)
Treatment of ICD?
- Avoidance of the irritants
- Moderately potent topical CS & emollients
Allergic Contact Dermatitis (ACD) etiology
Delayed hypersensitivity (type IV).
Allergic Contact Dermatitis (ACD) Criteria
- There must be a previous contact to induce the allergy > contact or ingestion (nickel (present in plants)).
- Specific to 1 chemical & its close relatives.
- After allergy has been established, all areas of skin will react to the allergen.
- Sensitization persists indefinitely
- Desensitization rarely possible
Allergic Contact Dermatitis (ACD) Suspected if:
- If certain areas are involved (eyelids, external auditory meati, hands, feet, and around gravitational ulcers).
- There is a known contact with the allergens.
- Individual’s work carries a high risk. (ACT is especially common in metal workers, hairdressers, healthcare workers, cleaners, painters and florists)
- Patients with atopic dermatitis associated with defective Filaggrin (structural protein in the stratum corneum) have a high risk of also developing ACT.
- For some substances 1 exposure is enough for sensitization & other need prolonged exposure.
- It is more common in female more than male, due to nickel allergy (earring and jewelry) and recently from acrylate allergy associated in nail cosmetics.
- Many young children are also allergic to nickel.
- It is specific to one chemical and its close relatives.
- After allergy has been established, all areas of skin will react to the allergen.
Allergic Contact Dermatitis (ACD) Pathogenesis
- The T cells that are involved are memory cells derived from prior stimulation of same antigen.
- The mechanism involves CD4+T lymphocytes which recognizes an antigen on skin surfaces, releasing cytokines that activate the immune system.
Presentation of ACD
Affected skin may be:
- Red and itchy.
- Swollen and Blistered.
- Dry and bumpy.
ACD Investigations
Patch testing > gold standard.
- Done on back.
- Detect type IV hypersensitivity.
ACD treatment
Avoidance
Job changes
Topical CS
