Phenotypic and Molecular Characterisation of Cerebral Amyloid Angiopathy

Inclusion Criteria: * Patients with a diagnosis of cerebral amyloid angiopathy (CAA) whose genetic samples are initially sent to the Rouen or Paris-Lariboisière genetics laboratories for molecular diagnosis of a genetic cause, thanks to national recruitment and for whom the patients consent to continuing genetic analyses for research purposes without feedback. * Diagnosis of cerebral amyloid angiopathy (CAA) certain or probable according to the modified Boston diagnostic criteria (1) (except age) * Age of onset of symptoms \<66 years * Absence of APP mutation/duplication (analysis must already have been carried out in the laboratory on receipt of the sample as part of routine care) * Signed consent for research * Patient covered by a social security scheme Exclusion Criteria: * Age at first neurological symptom \> 66 years * Minor patients * Other differential diagnosis that better explains the clinical situation * Identification of mutations or duplication of the APP gene * AAC possible but not probable according to the revised Boston criteria * Patient deprived of liberty by judicial or administrative decision