pre-IC5

Question 1

What is an allergy?

Answer 1

An immunologically mediated hypersensitivity reaction to a substance in a sensitised person.

Question 2

How is hypersensitivity different from an allergy?

Answer 2

It is not proven to be a/w an immune response

Question 3

Possible cause of hypersensitivity

Answer 3

Drugs can cause the release of mast cell and basophil-derived mediators by a pharmacologic/ physical effect rather than IgE

Question 4

Examples of hypersensitivity reactions

Answer 4

1. Vancomycin: ‘Red man syndrome’ -> direct release of histamines
2. ACE/ Sacubitril: Angioedema -> Inhibition of bradykinin
3. NSAIDs: NSAIDs induced asthma -> Alter metabolism of prostaglandins

Question 5

What is anaphylaxis?

Answer 5

It is an acute, life threatening reaction which involves multiple organ systems.

Question 6

Signs of anaphylaxis + frequency

Answer 6

1. Skin (hives, urticaria): 80-90% of reactions
2. Airway (tightness + swelling of throat, hoarseness, scratchy throat, trouble breathing, wheezing, chest tightness): 80-90% of reactions
3. GI tract (nausea, vomiting, abdominal cramps, diarrhoea): 30-45% of reactions
4. CVS (chest pain, low blood pressure, rapid heart rate (+ weak pulse)): 30-45% of reactions
5. CNS (anxiety, headache, dizziness, confusion, tunnel vision, fainting): 10-15% of reactions

Question 7

When is the risk of fatal anaphylaxis the greatest?

Answer 7

During the first few hours

Question 8

Most commonly reported drugs causing anaphylaxis

Answer 8

NSAIDs, penicillin and insulins

Question 9

Examples of clinical manifestations of hypersensitivity

Answer 9

1. Serum fever/ drug fever due to circulating immune complexes (Antibiotics)
2. Drug-induced autoimmunity e.g. haemolytic anaemia from methyldopa/ hepatitis from phenytoin
3. Vasculitis due to inflammation and necrosis of blood vessel walls; may be limited to skin or involve multiple organs(allopurinol&thiazide)
4. Asthma from NSAIDs
5. Acute infiltrative and chronic fibrotic pulmonary reactions from bleomycin/ nitrofurantoin
6. Eosinophilia, haemolytic anaemia, thrombocytopenia, agranulocytosis

Question 10

What is serious cutaneous adverse reaction (SCAR)?

Answer 10

Includes drugs rash with eosinophilia and systemic symptoms (DRESS), and mucocutaneous disorders: Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN)

Question 11

What is the common cause of DRESS, its symptoms and mortality rate?

Answer 11

Common cause: Allopurinol/ Anticonvulsants
Symptoms: Triad of rash, eosinophilia & internal organ involvement
Mortality rate: 10%

Question 12

What is the common cause of SJS/TEN, its symptoms and mortality rate?

Answer 12

Common cause: Antibiotics esp sulfonamides
Symptoms: Progressive ‘blistering’ disorders that constitute dermatologic emergencies -> progress to include mucous membrane erosion and epidermal detachment -> SJS < 10% detachment of body surface area; TEN > 30%
Mortality rate: SJS (1-5%); TEN (10-70%)

Question 12

What is the common cause of SJS/TEN, its symptoms and mortality rate?

Answer 12

Common cause: Antibiotics esp sulfonamides
Symptoms: Progressive ‘blistering’ disorders that constitute dermatologic emergencies -> progress to include mucous membrane erosion and epidermal detachment -> SJS < 10% detachment of body surface area; TEN > 30%
Mortality rate: SJS (1-5%); TEN (10-70%)

Question 13

4 types of hypersensitivity

Answer 13

Type I: Immediate hypersensitivity (mast cell derived mediators & cytokine-mediated inflammation)
Type II: Antibody-mediated diseases
Type III: Immune complex - mediated diseases
Type IV: T cell-mediated diseases