Introduction Amyloid is a proteinaceous substance made of fibrils that are shown by electron microscopy to be 8–10 nm wide and are composed of insoluble peptides. In all types of amyloid, the peptides, which derive from precursor proteins, change their secondary structure into β-sheet-rich structures. The accumulation of amyloid may occur extracellularly or intracellularly. In the brain, extracellular amyloid may appear as deposits in the parenchyma (amyloid plaques) or within the vessel wall (cerebral amyloid angiopathy [CAA]). Cerebral amyloid angiopathy is the neuropathological hallmark of biochemically and genetically diverse disorders characterized by the presence of amyloid in the walls of arteries and, in some cases, in capillaries of the brain parenchyma and leptomeninges [1–4]. This accumulation may represent the failure of vessels in eliminating soluble forms of amyloidogenic peptides from the brain . The amyloidogenic peptides found in cases of CAA are listed in Table 13.1. Among CAAs, amyloid-β (Aβ) CAA (Aβ-CAA) is the most common and is frequently present in sporadic and genetically determined Alzheimer’s disease (AD) and in some forms of hereditary cerebral hemorrhage with amyloidosis (HCHWA), and may also occur in non-demented individuals [1, 2, 5]. Cerebral amyloid angiopathy is also found in association with mutations in the prion protein (PRNP), BRI2, transthyretin (TTR), cystatin C (CST3) and gelsolin (GSN) genes [2, 6–11]. Here, we will describe the most significant clinicopathological characteristics of these CAAs, classified according to the amyloid protein involved.
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