The term vasculitis covers a number of probably autoimmune conditions in which there is inflammation of blood vessels. Small-vessel vasculitis (SVV) commonly affects glomeruli. Medium or large-vessel vasculitis alone will only cause renal disease if arterial involvement leads to hypertension or renal infarction.

ANCA are antibodies to neutrophil cytoplasmic antigens, granule enzymes such as myeloperoxidase and proteinase 3. They are useful but not completely reliable guides to the diagnosis of systemic vasculitis.

The glomerulonephritis of SVV may be accompanied by involvement of other organs. In severe disease crescentic nephritis (rapidly progressive glomerulonephritis, RPGN; see glomerulonephritis) may occur in combination with lung haemorrhage. Any other organ may be involved; skin and gastrointestinal involvement are perhaps the most common.  However in a significant proportion of patients the kidneys seem to be the only major organ affected at the time of diagnosis.  Although most patients have acute disease, the diagnosis is sometimes picked up unexpectedly in patients with slowly progressive kidney disease.

SVV may occur at any age, but the majority of cases are in elderly patients. Many cases progress over months. However acute and life-threatening disease also occurs and seems a more likely presentation in young patients.

SVV is a serious diagnosis.  Without treatment it is usually progressive, and it may be fatal through causing renal failure, gastrointestinal haemorrhage, stroke, or other involvement. Involvement of other organs may indicate the underlying subtype of vasculitis, e.g. ENT and lung complications in Wegener’ disease.

Treatment of SVV with cyclophosphamide, corticosteroids and plasma exchange can salvage renal function even if the patient is oliguric, and this is usually the favoured treatment in anyone with aggressive disease.  Other cytotoxics (MMF; methotrexate in non-renal disease) may be used in some circumstances.

Case history: A 73 year old woman became non-specifically unwell over a period of several weeks. She then developed arthralgias without visible joint swelling. 7kg weight loss was noted. 3 weeks before admission blood tests showed a mild anaemia, moderately elevated erythrocyte sedimentation rate, mild renal failure (urea 7 mmol/l, creatinine 138 micromol/l), and she was referred to a rheumatologist. Before attending that appointment she became increasingly breathless over 24h. On admission she had bilateral lung shadowing and crackles without evidence of heart failure, fluid retention or infection, though she had a mild pyrexia. Urea had risen to 20 mmol/l and creatinine to 420 micromol/l. Urine testing showed blood +++, protein ++. Fresh haemoptysis developed and oxygenation worsened. She became oliguric and soon required dialysis and assisted ventilation. In the absence of evidence of infection or other cause, a suspicion of systemic small vessel vasculitis was supported by positive ANCA (anti-myeloperoxidase specificity). A later renal biopsy showed crescentic nephritis. Treatment with cyclophosphamide, prednisolone and plasma exchange led to rapid improvement in lung pathology and slower improvement in renal function. Dialysis was discontinued after two weeks. One year later she was taking azathioprine 100mg, prednisolone 10mg daily, had a creatinine of 160 micromol/l, and was well.

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