Sporadic and Familial Cerebral Amyloid Angiopathies

Cerebral amyloid angiopathy (CAA) is the term used to describe deposition of amyloid in the walls of arteries, arterioles and, less often, capillaries and veins of the central nervous system. CAAs are an important cause of cerebral hemorrhage and may also result in ischemic lesions and dementia. A number of amyloid proteins are known to cause CAA. The most common sporadic CAA, caused by Aβ deposition, is associated with aging and is a common feature of Alzheimer disease (AD). CAA occurs in several familial conditions, including hereditary cerebral hemorrhage with amyloidosis of Icelandic type caused by deposition of mutant cystatin C, hereditary cerebral hemorrhage with amyloidosis Dutch type and familial AD with deposition of either Aβ variants or wild‐type Aβ, the transthyretin‐related meningo‐vascular amyloidoses, gelsolin as well as familial prion disease‐related CAAs and the recently described BRI2 gene‐related CAAs in familial British dementia and familial Danish dementia. This review focuses on the morphological, biochemical, and genetic aspects as well as the clinical significance of CAAs with special emphasis on the BRI2 gene‐related cerebrovascular amyloidoses. We also discuss data relevant to the pathomechanism of the different forms of CAA with an emphasis on the most common Aβ‐related types.