Urticaria Flashcards
Urticaria vs angioedema
Urticaria has edema in the superficial dermis and is well demarcated. Angioedema has edema in the deep dermis or subq and is poorly demarcated
Ddx of urticaria
BP DH Drug eruption Erythema marginatum Erythema multiforme Papular urticaria Pruritic urticaria papules and plaques of pregnancy Stills disease Urticaria pigmentosa Urticaria vasculitis
Time duration of ordinary and delayed pressure urticaria
4-36 hours
Time duration of physical urticaria
30 minutes to 2 hr
Time duration of contact urticaria
1-2 hrs
Time duration of urticarial vasculitis
1-7 days
Chronic vs. acute urticaria
6 weeks
What are the three mechanisms for histamine release leading to acute urticaria
IgE often due to foods/drugs/inhalants
Complement/immune complex mediated often due to blood products
Nonimmunologic via drugs like aspirin and NSAIDs or histamine containing foods
What medications exacerbate chronic urticaria
Aspirin/NSAIDs, penicillin, ACE-I, opiates, EtOH, febrille illness, and stress
What systemic illness should you screen for in chronic urticaria
Thyroid autoimmunity, especially in females (can treat even if hypo or euthyroid)
DDx of chronic urticaria
Cutaneous lupus, urticarial vasculitis, urticaria pigmentosa, Sweets, Fixed drug eruption, BP, Muckle-Wells (urticaria, deafness, amyloidosis), Schnitzler syndrome (nonpruritic urticaria, IgM gammopathy)
MOA of antihistamines
Do not block the release of histamine, but inhibit its vasodilation and vessel fluid loss
Tx options in chronic urticaria
Anti-histamines, Doxepin, steroids, Leukotriene modifiers
3rd line agents: IVIG, methotrexate, and omalizumab
Physical urticaria subtypes
- Aquagenic
- Cholinergic
- Cold
- Delayed pressure
- Dermatographism
- Exercise induced
- Solar
- Vibratory
Timeframe of most physical urticarias
Brief. attacks lasting 30-120 minutes
Dariers sign
Exaggerated triple response seen in dermatographism
- red line w/in 15 sec
- broadening erythema
- wheel with surrounding erythema replaces red line
Pressure urticaria tx
Usually required prednisone, antihistamines not as effective
Presentation of cholinergic urticaria
round papular wheels that appear after exercise
How to differentiate cholinergic urticaria from exercise induced anaphylaxis
Hot water bath with induce the urticaria without the anaphylaxis
Two types of cold urticaria
Primary (children and young adults) and secondary acquired (people with previous primary cold urticaria who develop persistent wheels with vasculitis on bx)
Solar urticaria classification
Based on wavelength that induces the urticaria
Those reacting to >400gm wavelength will get hives even through glass
Aquagenic pruritus skin findings
None, just severe prickling skin discomfort
Tx with topical capsacin
Need to r/o polycythemia rubra vera
Syndromes of Angioedema
- Idiopathic recurrent
- Allergic
- Medication induced
- Hereditary (Type I,II, and III)
- Acquired (Types I and II)
- Episodic angioedema with eosinophilia (benign)
- Thyroid autoimmune
Hereditary antioedema substypes
Type I: C1 INH protein deficiency
Type II: C1 INH protein dysfunction
Type III: coagulation factor XII gene mutation
Acquired angioedema subtypes
Type I: lymphoproliferative dz consume C1 INH
Type II: auto-immune (anti C1 INH antibody)
Look for anti-C1q autoantibodies
Clinical presentation of hereditary angioedema
Late childhood or adolescence, family hx as it is autosomal dominant
Recurrent non-pitting, non-pruritic, non urticarial edema
W/u of suspected hereditary angioedema
measure serum complement 4, C1-INH (inhibitor)
Treatment of hereditary angioedema
Attenuated androgens: Danazol, Stanozolol, and oxandrolone
Contact urticaria syndrome types
Immmunologic (IgE mediated, can see associated rhinitis, laryngeal edema, and GI upset, can confirm dx via RAST)
Nonimmunologic (more common and benign, does not require pre-sensatization)
Pemphigoid Gestationis
self-limited, autoimmune usually presenting in late pregnancy to immediate post-partum
Tx with steroids and antihistamines
Associated with prematurity and small for age babies
PUPPP (pruritic urticarial papules and plaques of pregnancy)
Most common in 1st pregnancy
begins in late 3rd trimester or immedicately postpartum
Begins on abdomen and may spread symmetrically to extremities (initial lesions may be confined to striae)
No complciations
Atopic eruption of pregnancy
pts with atopic background variable morphology (eczematous patches, prurigo nodules, etc)
Intrahepatic cholestasis
Itchy without rash (skin changes may be due to scratching)
Associated with increased bile acids
May recur with subsequent pregnancies
Increased risk of fetal demise, prematurity, fetal distress
Tx: ursodeoxycholic acid
Urticarial vasculitis clinical features
Urticaria last 1-7 days (rather than <24hrs)
Not itchy but complain of burning pain
Two subtypes of urticarial vasculitis
Normocomplement (idiopathic, benign, self-limited) and hypocomplement (more likely to have systemic sx/dz)
Serum sickness etiology
Following exposure to medication, monocloncal antibody, blood products, or animal derived vaccines
Type III hypersensitivity (immune complex) reaction where these complexes get trapped in vessel walls and activate complement
Serum sickness clinical presentation
Symptoms appear 8-13 days post exposure and last for 4 days
Morbilliform rash/urticaria are classically seen with fever, malaise, arthralgias, etc
Commonly implicated drugs in serum sickness
Penicillin, sulfas, Thiouracils, aminosalicylic acid, streptomycin, hydantoins, and cholecystographic dyes
