Urticaria and Drug Rashes Flashcards
What is urticaria?
rapid development of ‘hives’- itchy swellings of skin that results from inflammatory reactions mediated by release of histamine into skin, causing capillary leakage and edema (can be allergic or non-allergic in nature)
If an individual lesion lasts more than 24 hrs= probably not urticaria
What is this?
Urticaria- lesions tend to come and go over the course of a day. Note that you CAN get annular lesions
How long do the wheals of urticaria last?
A few hours before resolving. BUT you can get a series of these lesions that collectively last longer and may have associated angioedema (swelling of the deeper dermis and subQ tissue lasting up to 72 hrs)
What is ACUTE urticaria defined as?
Urticaria lasting less than 6 weeks (chronic=longer)
What are some things that cause acute urticaria?
- Infections (40%)- often URI
- Drugs (comes up right after taking drugs)
- Foods, Inhalants, Stress, Systemic Diseases
What drugs have been known to cause acute urticaria?
-B-lactams, NSAIDs, aspirin, opiates, contrast media
What things have been known to cause chronic urticaria?
Majority are idiopathic but can be caused by chronic infections, rheum disorders, and autoantibodies to IgE receptors on mast cells
How common is angioedema in urticaria?
common in up to 40% (especially food-induced urticaria) and typically involves the lips, periorbital areas, hands, and feet
What are some other causes of angioedema?
- C1 inhibitor deficiency (HANE)
- ACEIs
Some forms of urticaria are not immunologic and have a physical cause, such as:
Dermatographism (stratch of pressure causes hives)
Cold/heat urticaria
Solar/aquagenic
delayed pressure urticaria (common on waistband after sitting)
How is urticaria treated? What about angioedema/anaphylaxis?
Antihistamines is DOC (prevents more hives from forming than resolving the formed ones). May need several drugs or higher doses for chronic urticaria (LTRAs, H2-blockers)
angioedema/anaphylaxis: Epinephrine
Individual urticaria lasting more than 24 hrs suggests what?
urticarial vasculitis (biopsy needed)
Cutaneous DRUG rxns are more common in what patient populations?
- increasing age, female gender
- contaminant viral infections (HIV, EBV)
What are some common drugs that cause cutaneous drug rxns?
- ABX
- Anticonvulsants
- NSAIDs
What are the common patterns of drug induced rashes?
90% morbilliform rash (below) (5% urticarial)
NOTE: A morbilliform rash can also be the initial presentation of more serious rash, incuding toxic epidermal necrolysis, DRESS syndrome, and serum sickness
Describe morbilliform drug eruptions
Multiple, blanching, small, pink, ITCHY papules on the trunk and pressure-bearing areas that SPREAD OVER TIME TO BECOME CONFLUENT. These tend to last longer than urticaria
When does a morbilliform drug rash usually begin after starting a drug?
Usually 5-7 days after starting a drug (resolves spontaneously in 1-2 weeks, usually w/out complications). Urticaria will start IMMEDIATELY (type I hypersensivity)
What mediates morbilliform drug rxns?
Cell-mediated type IV hypersensitivity rxns (urticaria- type I)
Most common causes of morbilliform drug rxns?
penicillins, cephalosporins, sulfonamides, anticonvulsants
What is this?
urticarial drug rxns
Describe urticarial drug rxns
2nd most common form of cutaneous drug rxns and occur WITHIN MINUTES of exposure causes by IgE- mediated hypersensitivity (requires PRIOR EXPOSURE with AB exposure- thus, wont occur on very first exposure typically)
These appear more random than the patterned morbilliform pattern
What are the most common causes of urticarial drug rxns?
-penicillins, cephalosporins, aspirin, latex
What is DRESS?
Drug rash with eosinophilia and systemic symptoms (aka drug hypersensitivity syndrome)- a severe morbilliform drug rxn with eosinophilia and systemic illness that occurs 2-6 WEEKS AFTER EXPOSURE and TENDS TO LAST A LONG TIME AFTER DISCONTINUING THE DRUG
How does DRESS present?
- **facial edema characteristic**
- fever, LAD, joint pain
- multisystem involvement; liver common
