Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that gradually impairs memory, thinking, and behavior. It is the most common cause of dementia, a decline in cognitive function severe enough to interfere with daily life. The history of identifying AD began with a meticulous clinical case that linked a patient’s severe symptoms to unique physical changes in the brain. This discovery of pathological markers established the foundation for understanding this widespread public health concern.
The First Documented Patient
The formal history of the disease began in 1901 with the admission of Auguste Deter to the Frankfurt asylum in Germany. Auguste was 51 years old, an unusually young age for the severe mental decline she exhibited. Her symptoms included severe short-term memory loss, disorientation, and pronounced paranoia. She also displayed agitation and difficulty with language, often repeating phrases or being unable to write her name.
Dr. Alois Alzheimer, a psychiatrist at the asylum, took a deep interest in her case. He meticulously documented her clinical history and declining cognitive state over the five years she remained in the hospital. His detailed notes recorded her unpredictable behavior and profound confusion, which deteriorated until her death in April 1906.
Identifying the Disease
Following Auguste Deter’s death in 1906, Dr. Alzheimer requested her brain be sent to him in Munich for post-mortem analysis. Using newly available silver-staining techniques, he examined the brain tissue under a microscope. This examination revealed two distinct pathological features correlating with her severe symptoms. He found dense, abnormal clumps outside the nerve cells, later termed amyloid plaques. Inside the neurons, he observed twisted bundles of fibers, which he described as neurofibrillary tangles.
These microscopic hallmarks—amyloid plaques and neurofibrillary tangles—provided the first physical evidence linking a clinical syndrome to a unique brain pathology. Dr. Alzheimer presented his findings at a conference in November 1906, describing the case as a “peculiar severe disease process of the cerebral cortex.” Four years later, in 1910, his mentor, psychiatrist Emil Kraepelin, formally named the condition “Alzheimer’s Disease” in his textbook on psychiatry.
Establishing the Diagnosis
The initial diagnosis of Alzheimer’s disease was narrowly defined as a condition affecting only younger individuals, specifically those under the age of 65. Because Auguste Deter was 51 at the onset of her symptoms, the condition was classified as “presenile dementia.” This classification distinguished it from the more common “senile dementia” seen in the elderly, leading AD to be viewed as a rare disorder for several decades.
A significant shift in understanding occurred in the mid-to-late 20th century. Researchers demonstrated that the pathological hallmarks—the plaques and tangles—found in presenile AD were identical to those found in the elderly with senile dementia. This realization, summarized by American neurologist Robert Katzman in 1976, removed the arbitrary age distinction. The diagnosis was broadened, establishing Alzheimer’s disease as the most common cause of dementia in older adults.