Clinical Sciences

Question 1

HLA

Answer 1

HLA antigens are encoded for by genes on chromosome 6.

HLA-A3
haemochromatosis

HLA-B51
Behcet’s disease

HLA-B27
ankylosing spondylitis
reactive arthritis
acute anterior uveitis

HLA-DQ2/DQ8
coeliac disease

HLA-DR2
narcolepsy
Goodpasture’s

HLA-DR3
dermatitis herpetiformis
Sjogren’s syndrome
primary biliary cirrhosis

HLA-DR4
type 1 diabetes mellitus*
rheumatoid arthritis - in particular the DRB1 gene (DRB104:01 and DRB104:04 hence the association with DR4)

*type 1 diabetes mellitus is associated with HLA-DR3 but is more strongly associated with HLA-DR4.

Question 2

Complement Deficiencies

Answer 2

C1 inhibitor (C1-INH) protein deficiency
causes hereditary angioedema

C1q, C1rs, C2, C4 deficiency (classical pathway components)
predisposes to immune complex disease
e.g. SLE, Henoch-Schonlein Purpura

C3 deficiency
causes recurrent bacterial infections

C5 deficiency
predisposes to Leiner disease
recurrent diarrhoea, wasting and seborrhoeic dermatitis

C5-9 deficiency
encodes the membrane attack complex (MAC)
particularly prone to Neisseria meningitidis infection