We were also unable to test for amyloid precursor protein (APP) duplications in our patients, which are associated with early onset Alzheimer disease together with CAA.28, 29 However, patients with APP duplications described to date have presented with progressive cognitive impairment, making this an unlikely cause of the clinical syndromes of the patients described here, who all had initial symptoms related to intracerebral hemorrhages or seizures; additionally, there is no evidence of a family history suggestive of APP duplication for any of the cases described.28, 29, 30, 31, 32, 33. This evidence concerns the gene APP and early-onset autosomal dominant Alzheimer disease.