Large-scale APP duplication in early-onset Alzheimer's disease without cerebral amyloid angiopathy: A case report.

We present the case of a patient who began experiencing cognitive decline in her 30 s and was diagnosed with duplication of the amyloid precursor protein (Dup-APP) associated early-onset Alzheimer's disease (EOAD). The diagnosis was supported by the presence of amyloid and tau biomarkers. The clinical course, neuroimaging findings, and genetic testing excluded other diseases known to cause early-onset cognitive impairment. Our case exhibited a markedly large duplication of 19 Mb and did not present with cerebral amyloid angiopathy. Our findings suggest a potential association between the size of the duplication and the clinical phenotype.