Degenerative nerve diseases affect many of your body's activities, such as balance, movement, talking, breathing, and heart function. Many of these diseases are genetic. Sometimes the cause is a medical condition such as alcoholism, a tumor, or a stroke. Other causes may include toxins, chemicals, and viruses. Alzheimer's Disease (AD) has the largest burden of disease among all neurodegenerative disorders. AD is characterized by severe memory loss and cognitive deterioration, resulting in a complete dependency on others, and a greatly decreased life expectancy. In the brain, the roles of endosomes are relatively more complex due to the unique polar morphology of neurons and specialized needs for inter-cellular communication. Endosome function is altered in a surprising range of neurodegenerative disorders, including in several inherited neurologic disorders where the causative mutations occur in genes that regulate endosome function. In Alzheimer's disease (AD), endosome abnormalities are among the earliest neuropathologic features to develop and have now been closely linked to genetic risk factors for Alzheimer's disease.