Alzheimer Disease l: Introduction

Alzheimer disease is a chronic, progressive, and irreversible neurodegenerative disorder. It is the most common cause of dementia in older adults.

The disease is marked by extracellular neuritic plaques, intracellular neurofibrillary tangles, and gradual loss of neurons.

The etiology is multifactorial. Age is the main risk factor, and the prevalence roughly doubles every five years after age 65. Mutations in the APP, PSEN1, and PSEN2 genes are associated with early-onset familial Alzheimer disease, while the APOEε4 allele increases the risk of late-onset forms.

Modifiable risk factors such as head trauma, smoking, hypertension, and diabetes contribute to vascular injury, inflammation, and oxidative stress. Over time, these processes can damage neurons.

Clinically, the disease typically begins with short-term memory loss and difficulty learning new information. It then progresses to language deficits, disorientation, psychiatric symptoms including depression, and, in advanced stages, motor signs like a shuffling gait.