Dermatitis - Patel Flashcards
describe the appearance of skin in acute dermatitis
vesicular, bullous
describe the appearance of chronic dermatitis
red, scaly, lichenified with fissures, thickened
what is a common symptom of all types of dermatits
pruritus
for allergic contact dermatits (ACD), what is the pathogenesis
delayed type (type IV) T cell mediated hypersensitivity rxn
for the delayed type HSR seen in ACD, what are the 2 phases?
sensitization (induction) - req 10-14 days and elicitation (challenge) - re-exposure, dermatitis appears w/in 12-48 hours
what is the most common cause of ACD? what environmental allergens cause this? what is the chemical?
Rhus dermatitis
poison ivy, oak, sumac
urushiol - a resin
what is the 2nd most common cause of ACD?
nickel (think jewlery) that ain’t a igloo, that’s my watch and that ain’t snow baby thats my chain, that’s not ice girl, that’s my teeth and that’s not a snowcone, that’s my ring
ACD the main symptom is pruritis, what is the common presentation? appearance of their skin
eczematous, scaly edematous plaques w/ vesiculation distributed in areas of exposure
what is a key finding in the presentation of Rhus allergy
linear streaks unique distribution tells you it is contact from the external
what is the appearance of the lesions seen in Rhus allergy?
what do they start off as and what do they become? what forms after 1-2 days?
lesions begin as erythematous macules that become papules or plaques
blisters form over 1-2 days
treatment of SEVERE Rhus dermatitis? what about duration of this therapy and why?
oral steroids, especially if topical steroids are failing must give for 2-3 weeks - if given for less, pts may relapse
treatment of normal Rhus dermatitis
minor supportive care - topical steroids, oral or topical antihistamines - to improve pruritis, soothing shit like oatmeal baths and calamine lotion
what are the characteristics of eyelid allergic contact dermatitis
scaling red plaques on upper eyelids (lower less common) intensely pruritic caused by transfer from hands
common causes of eyelid allergic contact dermatitis
nail adhesive/polish
fragrances
nickel
for evaluation of dermatitis, what is a test to identify specific allergens?
patch testing
since not all pts w/ ACD need patch testing, when should you refer a pt for patch testing
when the allergen is unclear or the dermatitis is chronic
does a positive reaction of patch testing determine the cause of the pts rash? what confirms the clinical relevance of the positive patch test?
no - positive reaction does not mean the rash is due to that specific allergen
elimination of the rash with removal of the allergen confirms the clinical relevance of the positive patch test
this obviously dumb, but what is the number 1 treatment of ACD?
avoid exposure to the offending substance (big,bold, could be test question)
what are the 1st and 2nd most common locations that we talked about for nickel dermatitis?
bridge of nose and around the ears - from glasses
around the umbilicus - from belt buckles erythematous plaque with papules
what ACD can present with a delayed or immediate type HSR?
latex allergy
where does the dermatitis usually present for the delayed type of latex allergy
dorsum of hands
what are some other findings associated with the immediate HSR latex allergy?
disseminated urticaria, allergic rhinitis, and/or anaphylaxis
what are the two types of contact dermatitis?
allergic and irritant
define irritant contact dermatitis
ICD - inflammatory rxn in skin resulting from exposure to a substance that can cause an eruption in most people who come in contact with it NON-IMMUNOLOGIC
is previous exposure necessary in ICD
no
what is the general mechanism of causation in ICD
repeated application from mildly irritating substances (may occur from a single application w/ severely toxic substances, but this is not MC)
what type of disease is ICD? what 2 elements play a role?
multifactorial disease both exogenous (irritant and environmental) and endogenous (host) elements play a role
what is the most important exogneous factor for ICD
the inherent toxicity of the chemical for human skin
what are the most common sites on the body for ICD involvement and why (endogenous elements)
there are site differences in barrier function - skin is thinner
face, neck, scrotum, and dorsal hands more susceptible