small and medium vessel vasculitis Flashcards
What is purpura?
a skin rash resulting from BLEEDING INTO THE SKIN from small blood vessels. The individual purple spots are called petechiae. Purpura may be due either to defects in the capillaries (nonthrombocytopenic purpura) or to a deficiency of platelets (thrombocytopenia purpura) and clotting factors.
causes of purpura?
deficiency in clotting factors and platelets
problems in the vessel walls:
- steroids (decreased collagen production makes vessels more vulnerable to damage)
- vasculitis (cause vessel death)
- meningococcaemia (vessel death)
- thrombosis due to exposed TF and collagen (cause vessel death)
what do type 3 hypersensitivity reactions involve?
immune complex deposition (Ig + antigen). Complement becomes activated and neutrophils are attracted which kills blood vessels.
why is a patchy livedo important?
It indicated that there is vessel blockage around that area
what skin changes indicate vessel death?
blisters, necrosis and ulceration. It is important to consider whether a purpuric rash is simply RBC leakage or due to vessel death.
how do you differentiate between vasculitic and thrombotic skin changes
In vasculitis the purpura is palpable
a blue/purple edge around an ulcer implies what?
vasculitis
what is the characteristic histology?
These are not always present but generally
- inflammation with leukocyte infiltration
- fibrinoid necrosis of the blood vessel wall
- impairment of blood flow
- sometimes thrombosis
What are the clinical features of vasculitis? (non-specific and specific)
non-specific include weight loss, fever, night sweats
specific symptoms depend on the pattern of organ involvement
skin changes in vasculitis
lived reticularis purpura ulceration and gangrene digital infarction nodules
mucous membrane changes in vasculitis
oro-genital ulcers
nasal ulcers
eye signs in vasculitis
look out for pain, redness and photophobia
- scleritis
- episcleritis
- scleromalacia
what are the ANCA associated vasculitides?
GPA (granulomatosis with polyangitis) aka Wegeners (involves cANCA)
EGPA (Eosinophilic granulomatosis with polyangitis) aka Churg-Strauss syndrome (involves pANCA)
MPA (microscopic polyangitis) (involves pANCA)
What is ANCA?
Antineutrophil cytoplasmic antibodies (ANCA) are autoantibodies produced by a person’s immune system that mistakenly target and attack proteins within the person’s neutrophils (a type of white blood cell). ANCA testing detects and measures the amount of these autoantibodies in the blood. Two of the most common types or subsets of ANCA are the autoantibodies that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3).
cANCA/PR3 antibodies are most frequently seen in granulomatosis with polyangiitis and pANCA/ MPO antibodies are most often associated with microscopic polyangiitis. However, both may be seen in all three types with varying degrees of reactivity.
how are ANCA tests performed?
ANCA are autoantibodies produced by a person’s immune system that mistakenly attack proteins within the person’s neutrophils (white blood cell types). The most common subsets of ANCA are those that target the proteins myeloperoxidase (MPO) and proteinase 3 (PR3).
Two types of tests may be used:
Most often, ANCA tests are performed using indirect immunofluorescence microscopy (IFA). Serum samples are mixed with neutrophils to allow autoantibodies that may be present to react with the cells. The sample is put on a slide and treated with a fluorescent stain. The slide is then examined under a microscope and the resulting pattern noted. The cytoplasmic pattern (cANCA) is associated with PR3 antibodies and the perinuclear pattern (pANCA) is associated with MPO antibodies. Another possible pattern is atypical ANCA.
Myeloperoxidase antibodies and proteinase 3 (PR3) antibodies may be individually and specifically tested using an immunoassay method.
