Hypersensitivities 1-4 Part 1 Flashcards Preview

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What is physiology of a type 1 hypersensitivity?

Antigen exposure causes release of vasoactive substances such as histamine, prostaglandins, and leukotrienes from mast cells or basophils. This response is usually but not always IgE-dependent


What are examples of type 1 hypersensitivity

anaphylaxis, angiodema, bronchospasm, urticaria, allergic rhinitis (AR)


What is the physiology of type 2 hypersensitivity?

An antigen or hapten that is intimately associated with a cell binds to antibody, leading to cell or tissue injury


What are examples of type 2 hypersensitivies?

hemolytic anemia, interstitial nephritis


Explain how hypersensitivities are on a spectrum and how this affects a treatment plan?

Understand that hypersensitivity diseases, especially allergic reactions, manifest on a wide spectrum
A person may have minimal symptoms, or a person may have life-threatening symptoms!
Your approach to managing the patient will depend on where they lie on the spectrum


Describe in detail the process of type 1 IgE mediated disorders.

Immediate reactions that are triggered by binding of an allergen to a specific IgE that is found on the surface of a mast cell or basophil
Mast cells and basophils have granules that contain potent mediators of allergic reactions
During the sensitization or priming stage, the allergen-specific IgE antibodies attach to receptors on the surface of these mast cells and basophils
With subsequent exposure, the sensitizing allergen binds to the cell-associated IgE and triggers a series of events that ultimately leads to degranulation of the sensitized mast cell or basophil


What are the mediators of allergic reactions?

Acetylcholine-bronchiole smooth muscle contraction
Leukotrienes and Prostaglandins-more prolonged histamine like effects
Eosinophils-recruit more eosinophils


What are the 2 main subgroups IgE mediated allergy?

1. Atopy-state of being hyperallergenic (AR, asthma, allergic gastroenteropathy),

2. Anaphylaxis


What is urticaria?

hives-circumscribed wheals on a erythematous base on the skin, can be few mm-several cm, serpiginous borders, can last 12-24 hrs but generally shorter duration.


What angioedema?

related to urticaria but involving the deeper layers of the skin and generally manifests with facial, throat and tongue swelling.


What are some specific presentations of urticaria and angiodema?

dermatographisms (skin drawing), pressure urticaria, cold urticaria, cholinergic urticaria, aquagenic urticaria, solar urticaria


What is the main goal of the history questions regarding hypersensitivity?

To identify the specific cause or precipitant


What types of substances should be avoided that can aggravate hypersensitivities?

ASA, NSAIDS, ETOH, ACE inhibitors


What are some special considerations with chronic urticaria?

carefull with steroids (S/E can be worse than disease), educate the patient-often times cause is not found, many patients are free of lesions within a year, investigate thyroid and for H. Pylori, prescribe epipens with anyone with sever angioedema or anaphylaxis


Describe anaphylaxis

allergic, IgE-mediated and immediate hypersensitivity reaction to a protein substance. sx's develop in 5-60 mins


Describe anaphylactoid?

clinically presents the same as anaphylaxis but is caused by mast cell destruction and release of granule component


How will a patient with anaphylaxis present?

pruritis, flushing, impending doom, urticaria, angioedema, in 50% (sob, wheezing, laryngeal edema, can lead to respiratory failure), 30% shock from increased vascular permeability.


How do you manage someone with anaphylaxis?

It depends on severity but may include: intubation, large bore IV fluids, O2, epinephrine, antihistamines, bronchodilators, corticosteroids


What are common medication allergies?

beta-lactam antibiotics(penicillins, cephalosporins), sulfonamides (trimethoprim/sulfamethoxazole (Bactrim, Septra), phenytoin, carbazepine (Tegretol), allopurinol, NSAIDS


What are common drug allergy reactions?

urticaria, angioedema, anaphylaxis, exanthems (rash), vasculitis, exfoliative dermatitis/erythroderma, Steven Johnson's syndrome, erythema multiform, photosensitivity.


Whats important to remember in patients who claim to be allergic to penicillin?

Many of patients claiming to be allergic are actually able to tollerate treatment. Many are falsely labelled allergic.


What is the most important fundamental question to ask someone presenting with allergic reaction?

are there systemic reactions or sob?