Woman With Down Syndrome Had Alzheimer's Without Dementia in Surprise Case

Cognitive decline is a too-common feature of old age among those born with Down syndrome. Though the reasons aren't well understood, having an extra copy of chromosome 21 seems to hasten the neurodegeneration that puts individuals at risk of developing Alzheimer's disease. For the last decade of her life, and beyond, a US woman with Down syndrome mystified researchers by showing all of the physical signs of having Alzheimer's with none of the expected symptoms.