RGMA and Alzheimer disease: LDLR codes the low density lipoprotein receptor which is normally a cell surface protein.57,113 Mutations in this gene are associated with familial hypercholesterolemia.124 The link between LDLR genotypes and neuropathy with severe pain is not clear, but abnormal lipid metabolism is associated with neurologic conditions such as Alzheimer’s disease and RGMA (Repulsive Guidance Molecule BMP Co-Receptor A) genetic variants (see above) also affects lipid levels.125LDLR expression in the forebrain may affect BDNF levels126 possibly linking LDLR variants to psychiatric stress disorders.