A PSEN2 genetic test checks for disease variants in PSEN2, a gene that makes presenilin-2, a gamma-secretase part involved in APP processing. It measures single-gene Alzheimer risk, but it misses other genes, other dementia types, and most late-onset disease. Families often seek a second opinion after early memory loss or an unclear first diagnosis. Knowing what this test covers helps you bring the right history and ask for the right follow-up.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What does the test measure?
- Who benefits most in a second opinion?
- What can a result tell you?
- What does it miss and what should happen next?
What does the test measure?
The National Institute on Aging genetics fact sheet explains that PSEN2 on chromosome 1 encodes presenilin-2. Disease variants disrupt APP processing and increase longer amyloid-beta that forms Alzheimer plaques. Testing uses next-generation sequencing to find single-nucleotide and copy-number variants, according to Mayo Clinic Laboratories Insights. Labs often run it alone or as an APP, PSEN1, and PSEN2 panel.
A blood or saliva sample is enough for the lab work. Pathogenic variants cause autosomal-dominant early-onset familial Alzheimer disease, as described by MedlinePlus Genetics. A parent with the variant passes it to each child with a 50% chance. First-degree relatives therefore share the same risk decision.
Who benefits most in a second opinion?
Testing is most informative when symptoms start generally before age 65 plus a family shows an autosomal-dominant pattern. The ACMG/NSGC joint guidelines identify this group as the best fit for PSEN2 testing.
Bring these details to the second-opinion visit: Guidelines advise testing an affected relative first to confirm the family variant, according to the ACMG and NSGC joint practice guideline. A positive result in that person makes results clearer for others. Without it, a negative result in an unaffected person can mislead.
- ages of onset for affected parents, siblings, aunts, and uncles
- whether disease appears in every generation on one side
- prior genetic results for any affected relative
- current symptoms, timing, imaging, and lab work
What can a result tell you?
A positive PSEN2 result points to a strong single-gene cause for early-onset Alzheimer disease. It can explain a striking family pattern and focus care planning. It can also identify at-risk relatives who may want counseling. It cannot predict exact onset, severity, or progression.
ACMG/NSGC reports penetrance around 95%, while reviews report onset ranges from 40 to 75 and up to 45 to 88. Two people with the same variant can differ by decades. A negative PSEN2 result does not rule out dementia or a genetic contribution. The Continuum review notes unknown Alzheimer mutations still exist and most late-onset disease is polygenic. A specialist will keep looking when symptoms and history still suggest disease.
What does it miss and what should happen next?
PSEN2 testing misses causes specialists weigh in a second opinion. Mayo Clinic notes APOE risk alleles, sporadic late-onset Alzheimer, frontotemporal, Lewy-body, and vascular dementia need separate review. Those conditions require clinical exams, imaging, and broader panel evaluation.
Pre- and post-test counseling matters because results affect relatives, employment, and family planning. ACMG/NSGC guidelines require formal counseling and discourage predictive testing of asymptomatic minors. Ask for a genetics counselor referral before testing, and do not test a child to settle adult uncertainty.
