Genetic risk factors for the posterior cortical atrophy variant of Alzheimer's disease

Introduction The genetics underlying posterior cortical atrophy (PCA), typically a rare variant of Alzheimer's disease (AD), remain uncertain. Methods We genotyped 302 PCA patients from 11 centers, calculated risk at 24 loci for AD/DLB and performed an exploratory genome-wide association study. Results We confirm that variation in/near APOE/TOMM40 (P = 6 × 10⁻¹⁴) alters PCA risk, but with smaller effect than for typical AD (PCA: odds ratio [OR] = 2.03, typical AD: OR = 2.83, P = .0007). We found evidence for risk in/near CR1 (P = 7 × 10⁻⁴), ABCA7 (P = .02) and BIN1 (P = .04). ORs at variants near INPP5D and NME8 did not overlap between PCA and typical AD. Exploratory genome-wide association studies confirmed APOE and identified three novel loci: rs76854344 near CNTNAP5 (P = 8 × 10⁻¹⁰ OR = 1.9 [1.5–2.3]); rs72907046 near FAM46A (P = 1 × 10⁻⁹ OR = 3.2 [2.1–4.9]); and rs2525776 near SEMA3C (P = 1 × 10⁻⁸, OR = 3.3 [2.1–5.1]). Discussion We provide evidence for genetic risk factors specifically related to PCA. We identify three candidate loci that, if replicated, may provide insights into selective vulnerability and phenotypic diversity in AD.