Phases of symptom onset in familial Alzheimer’s disease
A Youngtimers Guide ・ Last Reviewed Nov 12 2025
Current science cannot identify precisely when familial Alzheimer’s disease (FAD) symptoms will begin. Right now, what biomarker blood tests can do is indicate which biological phase someone is in, and how quickly they are moving through the phase.
Think of it like a long road trip. The biomarkers do not give the exact minute of arrival. But they show how far the journey has gone, how fast things are moving, and whether traffic is building ahead.
The word we use for this in medicine is pathology. Pathology refers to the biological changes that happen in the body as a disease develops. It does not mean someone is sick in a visible or functional sense. In the context of Alzheimer's, pathology refers to the physical changes happening in the brain, such as amyloid plaques forming or neurons becoming stressed, that may be detectable through testing long before any symptoms appear.
These are the key phases that lead to symptom onset in familial Alzheimer’s disease.
Phase 1: Pre-pathology
The Alzheimer's process has not yet started yet.
What is happening biologically: The brain is not yet showing the biochemical changes associated with Alzheimer's. Amyloid is not accumulating. There is no measurable neuronal stress or injury.
What the tests show:
P-tau217: Normal or low
NfL: Low, or below average for age
GFAP: Normal for age
What this means for timing: Symptoms are unlikely in the next five or more years. This is the lowest-risk, lowest-urgency zone.
Testing cadence: Every 24 months is sufficient. More frequent testing in this phase adds anxiety without adding information.
What this phase is like for many people: This is a period of relative calm. Many members of the Youngtimers community in this phase focus on brain health, relationships, planning, and what matters most to them. The markers will signal if something changes.
Phase 2: Silent pathology
Amyloid is building. The brain is still coping.
What is happening biologically: Amyloid plaques have begun forming in the brain. The brain's compensation systems are still working well. There are no functional symptoms, and most people in this phase feel completely normal. This phase can last many years.
What the tests show:
P-tau217: Borderline or beginning to rise
NfL: Still stable or low
GFAP: May begin to rise modestly
Amyloid test: Borderline to positive
What this means for timing: Symptoms are often still three to seven years away, sometimes longer. The question shifts from "if" to "how fast." The rate of change in markers over time becomes the most important signal.
Testing cadence: Annually. Testing more frequently in this phase tends to generate noise rather than clarity.
What this phase is like for many people: Receiving meaningful information before any outward signs exist is both the gift and the challenge of early detection. Community support, counseling, and clear communication with a medical team matter more here than at almost any other point. Many members of the Youngtimers community find this phase easier to navigate when they are not facing it alone.
Phase 3: Transition phase
Pathology is present. Early injury is beginning.
What is happening biologically: Amyloid is established. Tau pathology is becoming more active, meaning abnormal tau changes are spreading beyond the initial sites. Neurons are beginning to show measurable stress. This is the most information-rich phase, and also the most emotionally significant.
What the tests show:
P-tau217: Rising, often clearly elevated
NfL: Showing a sustained upward trend year over year
GFAP: Elevated
Formal neuropsychological testing: Still mostly normal, but worth beginning
What this means for timing: The risk of symptoms entering the two-to-four year range increases as multiple markers rise together. No single marker crossing a threshold is the signal. Convergence of markers moving together is what matters most.
Testing cadence: Biomarkers annually. Formal neuropsychological testing every one to two years. This is also the phase where clinical trial eligibility often becomes most relevant.
What this phase is like for many people: This phase asks a great deal of people navigating it. It is also where knowledge is most powerful. Understanding what the markers are showing, and having a medical team that understands FAD specifically, makes an enormous difference. Many members of the Youngtimers community find this is the phase where connecting with others who have been through it matters most.
Phase 4: Early clinical symptoms
The brain's compensation is beginning to fail
What is happening biologically: Subtle cognitive changes begin to emerge. These may be noticed by the person themselves, by close family members, or detected through neuropsychological testing, often before they affect daily functioning significantly.
What the tests show: Biomarkers are no longer primarily predictive at this stage. They become confirmatory context, helping clinicians understand the biology behind what is now clinically visible.
What this means for timing: Symptoms have begun. The role of testing shifts from "how close are we" to "how do we manage what is happening and plan what comes next."
One important reality in this phase: It is common for the person experiencing early symptoms to be the last to recognize them. This is not stubbornness or denial. There is a neurological condition called anosognosia, in which the same brain changes that cause cognitive symptoms also impair the brain's ability to perceive that anything is wrong. A person can be genuinely, completely unaware that their memory or thinking has changed. It’s also common for a person with early-stage Alzheimer's to notice something is off, but minimize or rationalize it. Due to each of these possibilities, family members and close friends are often the first to notice a person’s Alzheimer’s symptoms.
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