Vasculitis and the reactive erythemas

Aetiopathogenesis

The CICs, which may be associated with several conditions ( Table 46.1 ), 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.

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. 46.1 ). Specific types are as follows:

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  Cutaneous small vessel vasculitis is defined by palpable purpura, usually on the lower legs. IgA deposition at the basement membrane ( Henoch – Schönlein purpura) often follows a streptococcal infection, occurs in approximately 50% of cases and is associated with internal involvement (arthritis, abdominal pain and haematuria), and mainly affects children. IgG/IgM CICs are unlikely to be associated with systemic involvement.

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  Microscopic polyangiitis (granulomas around vessels, perinuclear antineutrophil cytoplasmic antibodies [p-ANCA] positive), Churg-Strauss syndrome (no granulomas, p-ANCA positive, with eosinophilia and asthma) and granulomatosis with polyangiitis (GPA) (previously Wegener’s granulomatosis) are rare, commonly affect internal organs and present with systemic signs, nodules and palpable purpura, often with necrosis.

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  GPA is a potentially fatal granulomatous vasculitis of unknown cause. Malaise, upper and lower respiratory tract necrosis, glomerulonephritis and, in 40% of cases, a cutaneous vasculitis are found. Classical antineutrophil cytoplasm antibodies (c-ANCA) directed at proteinase 3 (PR3) are present.

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  Polyarteritis nodosa (PAN, ANCA negative) is characterized by a necrotizing vasculitis in medium-sized arteries and may be associated with hepatitis B. It is uncommon and afflicts middle-aged men who, in addition to tender subcutaneous nodules along the line of arteries, may develop hypertension, renal failure and neuropathy. Variants confined to the skin with livedo and nodules, predominantly on the lower legs, are known as cutaneous PAN or cutaneous arteritis and do not involve internal organs.

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  Giant cell arteritis affects medium-sized arteries in the elderly. Patients present with scalp tenderness due to temporal artery involvement that can progress to scalp necrosis. Treatment is prednisolone. Visual loss may result if untreated.

Non-immune complex causes of palpable purpura need exclusion and include paraproteins, cryoglobulins (e.g. with hepatitis C), systemic lupus and Sjögren’s syndrome.

Management

The cause is identified and remedied if possible. Some idiopathic cases settle with bed rest but, if lesions continue to develop and if internal organs are involved, treatment is indicated. Dapsone, 100 mg daily, is often effective for cutaneous vasculitis. Otherwise, prednisolone (sometimes with an immunosuppressive) is prescribed. Giant cell arteritis, PAN and GPA nearly always require oral steroids and immunosuppression.