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Vasculitis |
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Vasculitis syndromes are a mixed group of
diseases, affecting blood vessels of all types.
Vasculitis implies inflammation and damage to the vessel wall. It can affect
capillaries, venules,
arterioles, arteries and, occasionally, large veins.
In the most severe cases this leads to irreversible vessel wall destruction. In
mild cases the damage
is transient and may be marked only by cellular infiltration and vessel wall
damage manifest by
leakage of red blood cells.
There are three main groups of vasculitis syndromes:
1) Hypersensitivity vasculitis is the most common pattern. It affects
capillaries and venules, and is
usually manifest as a skin rash. It is often a manifestation of allergy to a
drug
('drug-induced vasculitis'), occasionally arising as an allergic rash in
viraemia or bacteraemia.
It also occurs in Henoch-Schnlein purpura, serum sickness, and cryoglobulinaemia.
2) Vasculitis can be a major element of multi-organ autoimmune diseases such as
systemic
lupus erythematosus (SLE) and rheumatoid disease.
3) Systemic vasculitides are an important group of diseases, characterized by
differing patterns of
vessel-wall destruction, which is of unknown causation, e.g. polyarteritis.
Many diseases have a vasculitis as a main, possibly causative, feature.
Lymphocytic vasculitis is an important feature of the systemic connective tissue
disorders,
particularly SLE.
Most of the severe vasculitides are characterized by the presence of neutrophils
in the vessel wall
(neutrophilic vasculitis). However, in some disorders the walls are disrupted by
lymphocyte infiltration
(lymphocytic vasculitis). This is particularly seen in SLE and mixed connective
tissue disease,
and is frequently observed during histological examination of skin and muscle
biopsies. Similar
lesions may be seen in the brain in SLE. Although lymphocytic vasculitis is seen
in most cases of
connective tissue disease, there may also be an acute neutrophilic vasculitis
similar to that described
above (hypersensitivity vasculitis).
Lymphocytic vasculitis may also be seen in some drug reactions, particularly in
the skin.
Hypersensitivity vasculitis commonly presents with petechial haemorrhagic
lesions in the skin
Hypersensitivity vasculitis} mainly involves the post-capillary venules, with
some
capillary involvement.
The pathogenesis is due to
immune complexes between an antigen and antibody becoming trapped in the walls
of venules.
These
activate complement, setting off a local acute inflammatory response, with
neutrophil chemotaxis.
Destruction of the vessel wall is mediated by release of neutrophil enzymes.
In many cases this pattern of vasculitis is associated with drug therapy or
infection. The extravasation
of red cells in the dermis is manifest as a transient palpable purpuric skin
rash,which disappears
when the drug is stopped or the infection passes. |
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We give here simplified and accurate information about the disease
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