Vasculitis and the reactive erythemas
Vasculitis and the reactive erythemas are characterized by inflammation within or around blood vessels. This may result from a type III hypersensitivity response, with circulating immune complexes, but other mechanisms are also possible.
Vasculitis
Aetiopathogenesis
The CICs, which may be associated with several conditions (Table 1), lodge in the vessel wall where they activate complement and cytokine release, attract polymorphs and damage tissue. Inflammatory cells infiltrate vessels. Endothelial cells may show swelling, fibrinoid change or necrosis.
| Group | Example |
|---|---|
| Idiopathic | 50% of cases (no cause found) |
| Blood disease | Cryoglobulinaemia |
| Connective tissue disease | Systemic lupus erythematosus, rheumatoid arthritis |
| Drugs | Antibiotics, diuretics, non-steroidals, anticonvulsants, allopurinol, cocaine |
| Infections | Hepatitis B, streptococci, Mycobacterium leprae, Rickettsia |
| Neoplasia | Lymphoma, leukaemia |
| Other | Wegener’s granulomatosis, giant cell arteritis, polyarteritis nodosa |
Clinical presentation
This depends on the size and site of the vessels involved. Vasculitis may be confined to the skin, or may be systemic and involve the joints, kidneys, lungs, heart, gut and nervous system. The skin signs are of palpable purpura, often painful and usually on the lower legs or buttocks (Fig. 1). Specific types are as follows:
Henoch–Schönlein purpura describes these signs, with arthritis, abdominal pain and haematuria. Direct immunofluorescence studies on a skin biopsy will show the small vessel immunoglobulin (Ig) A–CIC vasculitis, which can be helpful diagnostically. Mainly affects children and often follows a streptococcal infection.
