Hypersensitivity

Question 1

A 22 year old woman presents with an intermittently itchy and desquamating skin rash on her abdomen which is unresponsive to antihistamines.

Answer 1

Contact hypersensitivity: typical rash, in area where belt rubs.

Question 2

A 35 year old woman presents with a two day history of a red itchy skin rash which started soon after her first scuba-diving lesson. She is otherwise well.

Answer 2

Acute urticaria: suggestive rash, after ?latex.

Question 3

A&E, tongue swelling and acute respiratory tract obstruction. Blood pressure stable, Normal breath sounds. Medication includes cyclosporine, azathioprine, captopril and nifedipine.

Answer 3

Angioedema: no generalised allergic reaction. Most is drug-induced, mostly ACEi like captopril.

Question 4

Anaphylaxis Tx

Answer 4

500 micrograms adrenaline (0.5ml).
Under 12yo: 300 mcg
Under 6yo: 150 mcg

Question 5

Angioedema Tx (without anaphylaxis)

Answer 5

IV or IM antihistamines

Question 6

Non-autoimmune - Re-exposure, IgG, mast cells.

Answer 6

Type I hypersensitivity - allergy.

Question 7

Ab (IgG/IgM) to self

Answer 7

Type II hypersensitivity

Question 8

IgG/IgM immune complexes

Answer 8

Type III hypersensitivity

Question 9

Delayed response, T cell-mediated reaction

Answer 9

Type IV hypersensitivity

Question 10

Anaphylaxis

Answer 10

Mast cell degranulation:

• IgE mediated: peanuts, stings, penicillin, latex;
• non-IgE: NSAIDs, opioids, contrast, exercise.