Malignant hypertension can suddenly complicate and be superimposed on less severe, benign essential hypertension. The arterioles undergo concentric thickening and luminal narrowing with malignant hypertension, called hyperplastic arteriolosclerosis, and fibrinoid necrosis is a prominent feature. Fibromuscular dysplasia can involve the main renal arteries, with medial hyperplasia producing focal arterial obstruction. This process can lead to hypertension, but not typically malignant hypertension. Granulomatous arteritis is the most characteristic of anti-neutrophil cytoplasmic autoantibody (ANCA)-associated granulomatous vasculitis, which often involves the kidney but typically involves the lung and other organs. Hyaline arteriolosclerosis is seen with long-standing essential hypertension of moderate severity. These lesions give rise to benign nephrosclerosis. The affected kidneys become symmetrically shrunken and granular because of progressive loss of renal parenchyma and consequent fine scarring. Polyarteritis nodosa produces a vasculitis that can involve the kidney.