26th June 2023

Vasculitis

Inflammation and necrosis of blood vessel walls occur in many primary vasculitic disorders. Small vessel vasculitis is often associated with kidney disease due to the susceptible microcirculation of the kidneys. On histology, there is a focal inflammatory glomerulonephritis, usually with necrosis. Typically, the patient is unwell with an acute phase response, weight loss and arthralgia. In some patients, pulmonary haemorrhage may occur and can lead to respiratory impairment and/or death.

An important cause of renal impairment to exclude is ANCA-positive vasculitis. Anti-neutrophil cytoplasmic antibodies (ANCA) can attack the kidney tissue and lead to a deterioration in function. Subtypes of ANCA-positive vasculitis include:

• MPA (microscopic polyangiitis) – typically associated with renal dysfunction from glomerulonephritis and occasionally with pulmonary haemorrhage or gastrointestinal involvement.
• Granulomatosis with polyangiitis, formerly known as Wegener’s granulomatosis – typically involves the upper respiratory tract, the lower respiratory tract, and the kidneys. Upper respiratory tract involvement typically manifests as granulomas affecting the nasal passages and sinuses, causing nasal stuffiness, crusting, and epistaxis. Lower respiratory tract involvement manifests as granulomatous lung disease causing infiltrates, cavitating lesions, and pulmonary haemorrhage.
• Eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as Churg-Strauss syndrome, is another subtype of ANCA-positive small vessel vasculitis causing fever, sweating, weight loss, fatigue and hypereosinophilia. It is more common in patients with a history of allergic rhinitis and asthma. It can also be a cause of pulmonary haemorrhage.

PR3-ANCA (or cANCA) is most associated with Wegener’s granulomatosis, whereas MPO-ANCA (or pANCA) is most associated with microscopic polyangiitis. However, these are not specific, and biopsies should be obtained. Variation in the ANCA titres can be used in the assessment of disease activity.

The standard treatment of ANCA-positive vasculitis is with high dose steroids, cyclophosphamide, and mycophenolate. Glomerulonephritis secondary to vasculitis can also be seen in other conditions, such as cryoglobulinemia and SLE. Medium to large vessel vasculitis, such as polyarteritis nodosa (PAN), do not cause glomerulonephritis but can cause renal infarction if the renal blood vessels are involved.