CP5-4 diagnosis of autoimmune diseases Flashcards
How can an autoimmune disease develop?
The immune system should be tolerant to self antigens and eliminate parts of the immune system which attack itself. Failure to eliminate these autoimmune responses can lead to autoimmune disease.
What is sclerodactyly?
Tightening of the skin
How might scleroderma (systemic sclerosis) present?
Sclerodactyly
Livedo reticularis on the legs
Cool feet
What investigations can be dome for autoimmune diseases?
Test for:
ANA (antinuclear antibodies)
ANCA (antineutrophil cytoplasmic antibodies)
Creatine kinase
rheumatoid factor
Anti-CCP antibody
Complement
FBC, U&Es, LFTs and CRP
What is an ANA test?
An antinuclear antibody test which can be made more specific to identify subtypes of antibody that are binding to different bits of the cell nucleus
How does antinuclear antibody testing work?
By using indirect immunofluorescence - if fluorescence seen, the test it positive
What techniques can be used to identify dsDNA and ENAs in autoimmune disease?
Immunoblots
Individual ELISA’s
Microbead-based immunoassay
What antibodies are tested for in ANA screening?
dsDNA
Chromatin
Ribosomal protein
SS-A (52 and 60)
SS-B
Sm
Sm/RNP
RNP (A and 68)
Scl-70
Jo-1
Centromere B
How can antibody tests help determine which autoimmune disease a patient has?
Different antibodies are associated with different autoimmune disease so once the antibody present is identified, we can compare to find which autoimmune disease is associated with this antibody.
What two criteria needs to be considered in diagnosing autoimmune disease?
Clinical criteria (signs and symptoms)
Immunologic criteria
What is rheumatoid factor?
Antibody (either IgM, IgG or IgA) which attacks/is directed against the Fc portion of IgG
Which diseases (other than rheumatoid arthritis) may come back positive for rheumatoid factor?
Diseases where polyclonal stimulation of B cells is seen
What antibody is a key one to test in diagnosing rheumatoid arthritis more so than rheumatoid factor?
Anti-CCP antibody aka ACPA
What does a positive ACPA result indicate about the disease?
It is more severe and erosive
When is an anti neutrophil cytoplasmic antibody (ANCA) test done?
When vasculitis e.g. renal or ENT is suspected
If a patient is positive for ANCA, what treatment is started asap?
Immunosupression
What are symptoms of granulomatosis with polyangitis?
can include:
Mouth ulcers
Conjunctivitis
Fatigue
Pyrexia
SoB and persistent cough
Haematuria
Hypertension
Rash
Diarrhoea +/- blood
What is tested for in suspected granulomatosis with polyangitis?
Cytoplasmic ANCA aka cANCA
Perinuclear ANCA aka pANCA
Which autoantibody most commonly leads to a positive cANCA test?
PR3 (90% of time)
Which autoantibody most commonly leads to a positive pANCA test?
MPO (70% of time)
Which autoantibody is ANCA positive in 50% of cases of Churg-Strauss syndrome?
MPO
What is the gold tankard test for diagnosis autoimmune disease?
Histopathology
What does reemergence of ANCA in a patient who was in remission and ANCA negative mean?
A flare up of disease
What is found in testing for primary biliary sclerosis?
Anti-mitochondrial Ab
What is found in testing for autoimmune hepatitis?
Anti-smooth muscle and anti-liver/kidney/microsal (LKS) antibodies
How are antibodies in autoimmune liver disease detected?
By immunofluorescence screening
Antigen specific ELISAs
What is found when testing for type 1 diabetes?
Islet cell antibodies
Anti-GAD65 and anti-GAD67
IA-2
IAAs
What is found in a positive test for addisons’s disease?
Auto antibodies targeting adrenal cortex
What is detected when a patient has pernicious anaemia?
H+K+-ATPase in gastric parietal cells
What antibodies are found with autoimmune gastritis associated pernicious anaemia?
Antibodies to GPC and intrinsic factor
