List III - Core clinical problems for the student and new doctor

Question 1

What are the different types of hypersensitvity reactions?

Answer 1

• Type I - Anaphylaxis
• Type II - Cell bound
• Type III - Immune complex
• Type IV - Delayed hypersensitivity

Question 2

What is the mechanism of a type I hypersensitivity reaction?

Answer 2

Mechanism
- Antigen reacts with IgE bound to mast cells

Examples

• Anaphylaxis
• Atopy (e.g. asthma, eczema and hayfever)

Question 3

What is the mechanism of a type II hypersensitivity reaction?

Answer 3

Mechanism
- IgG or IgM binds to antigen on cell surface

Examples

• Autoimmune haemolytic anaemia
• ITP
• Goodpasture’s syndrome
• Pernicious anaemia
• Acute haemolytic transfusion reactions
• Rheumatic fever
• Pemphigus vulgaris / bullous pemphigoid

Question 4

What is the mechanism of a type III hypersensitivity reaction?

Answer 4

Mechanism
- Free antigen and antibody (IgG, IgA) combine

Examples

• Serum sickness
• Systemic lupus erythematosus
• Post-streptococcal glomerulonephritis
• Extrinsic allergic alveolitis (especially acute phase)

Question 5

What is the mechanism of a type IV hypersensitivity reaction?

Answer 5

Mechanism
- T-cell mediated

Examples

• Tuberculosis / tuberculin skin reaction
• Graft versus host disease
• Allergic contact dermatitis
• Scabies
• Extrinsic allergic alveolitis (especially chronic phase)
• Multiple sclerosis
• Guillain-Barre syndrome

Question 6

What are the common differentials for groin masses?

Answer 6

• Herniae
• Lipomas
• Lymph nodes
• Undescended testis
• Femoral aneurysm
• Saphena varix (more swelling than a mass)

Question 7

What are the key questions to ask regarding groin lumps?

Answer 7

• Is there a cough impulse
• Is it pulsatile AND is it expansile (to distinguish between false and true aneurysm)
• Are both testes intra scrotal
• Any lesions in the legs such as malignancy or infections (lymph nodes)
• Examine the ano rectum as anal cancer may metastasise to the groin
• Is the lump soft, small and very superficial (lipoma)

Question 8

What are the important questions to ask regarding scrotal lumps?

Answer 8

• Is the lump entirely intra scrotal?
• Does it transilluminate (hydrocele)
• Is there a cough impulse (hernia)