11- Cutaneous Reaction Patterns Flashcards
Doxycyline is known to cause _____ and _____ reactions.
Photosensitivity and sunburn
This is dose-dependent and predictable.
In general, allergy testing or other diagnostic tests are not helpful in pinpointing the specific culptrit when a cutaneous drug eruption is suspected. What is the exception to this?
Exception is the skin-prick testing to detect IgE-mediated penicillin reaction.s
What is the appearance of urticaria? How long do they last?
Aka hives - pink edematous papules and plaques that occur on the skin.
Lesions migrate and individual lesions last less than 25 hours, though the reaction as a whole may last longer.
What are three forms of anaphylaxis? What are they caused by?
Urticaria, angioedema, and aphaphylactic shock.
IgE-mediated immediate hypersensitivity.
What isthe most commonly identified cause of acute urticaria?
Upper respiraoty infection (but most are idiopathic); Drugs cause 10%
How would you treat urticaria?
A non-sedating antihistamine such as loratidine, cetirizine, and fexofenadine - combined with sedating class H1 antihistamines (diphenhydramine, hydroxyzine).
What is the most common cutaneous drug eruption? What type of reaction is this?
Exanthematous drug eruptions - aka morbiliform drug rashes
Type 4 (delayed) hypersensitivity
What do Exanthematous drug eruption lesions look like?
Monomorphic (invidiual lesions look like each other) macules and thin papules that start on the face and trunk and spread to extremities.
Usually pruritis and a low grade fever may occur.
What is the onset of exanthematous drug eruption? How do you treat it?
Usually 2-14 days after drug initiation, sometimes starting even after discontinuation.
They typically resolve on their own over 1-2 weeks, even with continuation of the drug. Treatment is supportive for the pruritis (topical corticosteroids and oral antihis.)
What is DRESS? What are associated symtpoms?
Drug reaction with eosinophilia and systemic symptoms.
Resembles exanthematous drug eruptions, but is commonly associated with fever.
Facial edema, enlarged noes, and arthralgias may also occur.
What is characteristic of DRESS but isn’t always present? What is the most common site of involvement in DRESS?
Eosinophilia characteristic but not always present.
Most common site: liver, seen with incresed hepatic enzymes.
Also myocarditis, pneumonitis, nephritis, thyroiditis, and brain involvement seen.
DRESS is fatal in ____% of patients. What is required to treat it?
Fatal in 10%
Systemic corticosteroids are required to treat most cases
What disease is characterized by targetoid lesions seen on acral sites?
Erythema multiforme - historically through to represent a spectrum of diseases with the same disease process as SJS and TEN but is now through to be a distinct disorder.
Describe the lesions seen on someone with erythema multiforme? How long do they last?
Target lesions with 3 or more color zones and dusky red or purple center.
They arise abruptly on acral areas and last up to 2 weeks.
What causes erythema multiforme?
Infectious triggers (most commonly HSV) make up 90% of cases
Drugs make up <10% of reactions
What cutaneous findings are seen with leukocytoclastic vasculitis?
Palpable purpura, usually more common on the legs.
Urticarial lesions may be seen but unlike true uticaria, these are fixed for >24 hrs.
Other possibilities: nodules, ulceration, livedo reticularis (purple, lacy, net-like pattern).
What do lesions from henoch-schlonlein purpura look like?
Main findings: palpable purpura on skin, especially on the buttocks and lower extremeties.
Also possible: arthritis, abdominal pain, GI bleeding, and nephritis.
