Polyarteritis nodosa

Polyarteritis nodosa

Cause

This necrotizing vasculitis of large arteries causes skin nodules, infarctive ulcers and peripheral gangrene.

Immune complexes may initiate this vasculitis, and sometimes contain hepatitis B or C virus or antigen. Other known causes are adulterated drugs, B-cell lymphomas and immunotherapy.

Presentation

Tender subcutaneous nodules appear along the line of arteries. The skin over them may ulcerate or develop stellate patches of purpura and necrosis. Splinter haemorrhages and a peculiar net-like vascular pat-tern (livedo reticularis) aid the clinical diagnosis. The disorder may be of the skin only (cutaneous polyarteritis nodosa), or also affect the kidneys, heart muscle, nerves and joints (Fig. 8.15). Patients may be febrile, lose weight and feel pain in the muscles, joints or abdomen. Some develop peripheral neuro-pathy, hypertension and ischaemic heart disease. Renal involvement, with or without hypertension, is common.

Course

Untreated, systemic polyarteritis nodosa becomes chronic. Death, often from renal disease, is common, even in treated patients.

Differential diagnosis

Embolism, panniculitis and infarctions can cause a sim-ilar clinical picture. Wegener’s granulomatosis, allergic granulomatosis, temporal arteritis, and the vasculitis that accompanies systemic lupus erythematosus and rheumatoid arthritis should be considered.

Investigations

The laboratory findings are non-specific. An elevated ESR, neutrophil count, and gammaglobulin level are common. Investigations for cryoglobulins, rheumatoid factor, antinuclear antibody, antineutrophil antibod-ies and hepatitis C and B surface antigen are worth-while, as are checks for disease in the kidneys, heart, liver and gut. Low levels of complement suggest active disease. The use of biopsy to confirm the diagnosis of large vessel vasculitis is not always easy as the arterial involvement may be segmental, and surgery itself difficult. Histological confirmation is most likely when biopsies are from a fresh lesion. Affected vessels show aneurysmal dilatation or necrosis, fibrinoid changes in their walls, and an intense neutrophilic infiltrate around and even in the vessel wall.

Treatment

Systemic steroids and cyclophosphamide improve chances of survival. Low-dose systemic steroids alone are usually sufficient for the purely cutaneous form.