Dermatitis Flashcards
What are the two phases of dermatitis?
Acute and chronic
State the features of the acute phase
- papulovesciular
- erythematous lesions
- oedema
- ooze/scale/crust
State the features of the chronic phase
- lichenification
- elevated plaques
- increased scaling
- risk of infection
What is the typical clinical sign of dermatitis?
itchy, ill defined erythematous, scaly patches
Name the different types of dermatitis
- contact allergic dermatitis
- irritant contact dermatitis
- atopic eczema
- discoid
- photosensitive
- seborrhoeric
- pampholyx
- eczema herpeticum
- lichen simplex
What is the pathology of contact allergic dermatitis on first exposure?
Type 4 hypersensitivity reaction where langerhans cells in the epidermis process an antigen and bind the antigen to MHC class II this cell travels to the lymph nodes to activate T cells - T cells then release cytokines which active macrophage leading to proliferation of allergen specific memory T cells
What happens on future exposure in contact allergic dermatitis?
T cells migrate to the site and cause inflammation
How is contact allergic dermatitis diagnosed?
Delayed hypersensitivity using patch test
How is contact allergic dermatitis treated?
Identify and avoid allergen
Steroids may be used to treat a flare
What is irritant contact dermatitis?
Non-specific physical irritation as a result of toxic effect of an irritant, strips the oils off the hand leading to symptoms
What are common irritants that cause ICD?
Soap, oil cleaning products
Where does ICD commonly occur?
Hands and finger web spaces
What is meant by atopic?
Word used to describe a group of diseases (asthma, eczema, hay fever and food allergy), that result from a tendency to develop hypersensitivity to allergens
What causes atopic diseases?
Genetic predisposition in addition to environmental factors
Describe the pathogenesis of acute atopic eczema
TH2 cells are activated by the presentation of antigens by langerhans cells to CD4+ cells in the dermis. TH2 cells release interleukin 4, 5, & 13 which recruit B cells and eosinophils. The B cells make IgE leading to mast cell degranulation.