Dermatitis Flashcards
What are the two types of contact dermatitis and are they mutually exclusive?
- Allergic contact dermatitis - allergic response caused by contact with a substance
- Irritant contact dermatitis -irritation to the skin by contact with a chemical or physical irritant
Not mutually exclusive -> processes can occur simultaneously in some patients
What type of reaction is an allergic contact dermatitis (ACD) and what are the two phases?
Cell mediated, delayed type IV hypersensitivity reaction
- Sensitization phase - allergen penetrates epidermis, presented by Langerhaans cells to T-cells, takes 1-14 days
- Elicitation phase - re-exposure to allergen activates T-cell response in hours to day
How long can ACD persist after antigen removal? How is it diagnosed?
Up to 3 weeks after removal of agent
Diagnosed via patch testing to identify allergen
What are common allergens which are associated with the Type IV hypersensitivity of ACD?
- Urushiol (poison ivy)
- Nickel jewelry
- Neomycin / bacitracin
- Black hair dye
What does ACD look like acutely and chronically?
Acutely - bright red / erythematous
Chronically - xerotic, fissured, lichenified eczematous plaques
In addition to the common allergens for ACD, what are some common causes which can lead to ACD on the eyelids?
- Cosmetics
- Nickel eyelash curlers
- Antibiotic eyedrops
- Nailpolish removers
- Eyelash adhesives
- Hair dyes
How is ACD treated? How long does it take before skin barrier function has normalized?
- Exposure avoidance
- Topical corticosteroids
- If severe, oral corticosteroids with at LEAST 14 day taper (prevent rebound symptoms)
- Emollients / moisturizers since barrier function takes 4 months to normalize
What is the most common form of contact dermatitis?
Irritant contact dermatitis (ICD). It is also the majority of occupational dermatitis
What causes ICD?
Non-immunologic response to chemical / physical agents, i.e.:
Soap, industrial cleansers, frictional forces
-> risk factors are occupations with repeated exposures to water, soaps, and solvents
How does acute ICD appear? Common locations?
Usually well demarcated (borders of where irritant touched) erythematous and scaly patches and plaques
Severe disease can develop vesicles and bullae
Common locations: Hands, forearms, eyelids, face
How does chronic ICD appear? Who would tend to get it?
Less erythematous, more lichenified than acute ICD. Often fissuring, scaling, and hyperkeratosis
Tends to occur with chronic exposures to solvents -> i.e. housewives
How is ICD managed?
Using more gloves, reducing exposure as much as possible, watching hands in cool / tepid water rather than hot which strips oil out of hands, topical steroids if needed.
What is eczema also called? What other conditions are associated with it?
Atopic dermatitis
Tends to happen in people who have a FHx of:
- Asthma
- Hay fever
- Eczema
Occurs in industrialized urban areas more
What gene is commonly mutated in patients with eczema, and what are they at increased risk for?
Filaggrin, a gene required for proper barrier function of the skin
Increased infection risk due to lack of proper barrier function
-> S. aureus, molluscum, HSV, HPV
What antibody tends to be elevated in atopic dermatitis, and do elimination diets tend to help?
IgE antibodies are high since it is associated with other IgE-related conditions, and eczema is thought to be partially Type 1 hypersensitivty
Dietary modifications do not help
What is the morphology of the rash in atopic dermatitis? Include chronic changes.
Red, crusted, scaly, pruritic plaques with vesicles and edema
If chronic: Lichenification and hyperpigmentation
Where does eczema appear in infants vs children / adults?
Infants - Face (esp. cheeks) and extensor surfaces since they are always lying on their back
Children / adults - Flexor extremities (antecubital and popliteal fossae), wrists, ankles
What is one big way to tell eczema apart from candidiasis or Letterer-Siwe (Langerhans cell histiocytosis)?
In eczema, the diaper area is spared.
It is heavily involved in these two conditions.
How does eczema look in skin of dark-skinned people?
Often appears brown or purple, with erythema apprecitated at periphery
Can leave post-inflammatory hyperpigmentation
What are possible simple or OTC options for treatment of eczema?
Avoiding triggers: i.e. dust mites and pollen
Repair skin barrier: moisturizers and lukewarm baths
Treatment of secondary infections with bleach bath
Antihistamines may have some utility
What are some prescription options for the treatment of eczema? Side effects?
- Topical steroids (ointments most potent) -> cutaneous atrophy
- Topical calcineurin inhibitors - pimecrolimus / tacrolimus -> black box warning of lymphoma
- Systemic steroids -> have high rate of relapse
- Phototherapy + systemic immunosuppressives -> UVA, narrow band UVB, MTX, AZA to calm immune response
What are serious infections which can arise in the setting of atopic dermatitis and how are they avoided / treated?
Staphylococcal - avoid with bleach paths, treat with antibiotics
VZV, HSV - Eczema herpeticum, treat with antivirals, but can be a dermatologic emergency requiring IV rehydration and antivirals
What disease is characterized by coin-shaped, scaly red/brown pruritis plaques with NO central clearing? What symptoms will the patient show?
Nummular dermatitis
Patient shows severe pruritis -> scratching often becomes habitual
Who tends to get nummular dermatitis and when is it thought to be worse? What is the treatment?
Tends to be in middle-aged and elderly. Disease is worse in the winter, due to impaired skin barrier function
Treatment is high dose steroids and moisturization
What is dyshidrotic dermatitis? How do the lesions appear?
Pruritic vesicular skin disorder of palms and soles, has nothing to do with sweat glands.
Lesions are very small and “tapioca-like” vesicles with minimal erythema. Typically occurs on lateral fingers.
What lab should you run for dyshidrotic dermatitis and nummular dermatitis?
KOH prep to ensure absence of dermatophytes
How does Lichen Simplex Chronicus (LSC) develop?
Occurs due to chronic rubbing / scratching of skin
-> often seen in patients with chronic, pruritic skin disease like atopic dermatitis, or systemic pruritis (end stage renal disease or liver disease (jaundice))
What does Lichen Simplex Chronicus look like? Where is it commonly found?
Lichenified, often hyper-pigmented plaques
Trunk, extremities, and scrotum is very common
What is the treatment for LSC?
Super potent steroid ointments, oral antihistamines (reduce itch), antidepressants if there is any psychological component to the itching.
Also help the patient identify habitual nature of itching and try to replace the compulsion with something else.
What is the cause of prurigo nodularis? What is the treatment?
Condition extremely similar to LSC, except it is due to chronic rubbing & picking
-> Treatment is exactly the same as LSC
What do lesions in prurigo nodularis look like?
Lichenified, hyperpigmented PAPULES and small plaques
-> lesions tend to be more nodular than LSC, and are more caused by picking than itching
