APOE and Alzheimer disease: Of these subtypes, the former has been associated with the ApoE ε2 allele and haemorrhagic imaging markers of CAA including lobar microbleeds and cSS.110 Non-haemorrhagic CAA is associated with the presence of ApoE ε4110; ApoE ε4 is also associated with capillary-level CAA as well as AD.111 Although it is tempting to consider the latter as a ‘cognitive’ CAA given these associations, evidence suggests that the situation is more complex than this.