The Diagnosis Your Doctor Might Be Missing: Understanding LATE

There is a conversation I have had a few times in the last several months in my resident clinic that I believe is worth blogging about. A family comes in — often adult children accompanying a parent in their mid-to-late eighties — and they describe a pattern that has been quietly unfolding for years. The memory has been slipping. Slowly. Names, recent conversations, why they walked into a room. But the person sitting across from me can still tell me where they vacationed in 1987. They can still do the crossword. They still know every face in the room. And when I look at their MRI, their hippocampus — the brain's primary memory-forming structure — is significantly atrophied (shrunken).

The family often assumes the answer is Alzheimer's. And for decades, so did most clinicians.

But in a meaningful number of these patients, the answer is something else entirely. It is a condition called LATE — Limbic-predominant Age-related TDP-43 Encephalopathy — and it may be one of the most underappreciated diagnoses in all of neurology.

What Is LATE?

LATE is a neurodegenerative disease driven by the abnormal accumulation of a protein called TDP-43. Under normal circumstances, TDP-43 is a housekeeping protein inside the nucleus of your cells, helping to regulate gene expression. In LATE, it misfolds, migrates out of the nucleus, and begins to accumulate as toxic deposits — primarily in the limbic system, the deep emotional and memory-processing regions of the brain that include the amygdala, the hippocampus, and the entorhinal cortex.

The result is a progressive amnestic syndrome — a slowly worsening memory disorder — that, on the surface, can look almost identical to Alzheimer's disease.

This is precisely what makes LATE so easy to miss.

How Common Is It?

This is where the numbers become genuinely important for any family navigating a dementia diagnosis in an older loved one.

LATE neuropathologic changes are found in roughly one-third of individuals aged 85 and older on autopsy. Among those in their nineties, it is considered the second most common neurodegenerative disease after Alzheimer's itself. A major multi-center analysis found that LATE is present in more than 10% of all individuals over age 65, and in 25% to 40% of those over 85.

These are not rare numbers. These are numbers that belong in every family medicine office and every memory clinic in the country. And yet, a validated blood test or imaging biomarker specific to TDP-43 — the kind of tool we now have for Alzheimer's amyloid — does not yet exist. Until recently, there were not even formal clinical criteria for diagnosing LATE during a patient's lifetime. A landmark 2025 paper published in Alzheimer's & Dementia by Wolk, Nelson, et al provided the first proposed framework for doing exactly that.

How Is LATE Different From Alzheimer's?

This is the question that matters most for families, and the answer is nuanced.

Both diseases attack the hippocampus. Both produce a profound loss of episodic memory — the "what happened yesterday" memories. Both can leave a person struggling to recall a recent conversation while perfectly preserving older, more deeply encoded memories. The clinical overlap is real and it is significant.

But several features point in the direction of LATE rather than Alzheimer's, and understanding them can change the entire trajectory of care.

Age of onset. LATE is predominantly a disease of the very old. It is uncommon before age 75 and becomes increasingly prevalent in the eighties and nineties. Alzheimer's, while also age-related, regularly presents in the late sixties and early seventies. If a patient's memory symptoms began after about age 80, LATE deserves serious consideration.

The pace of decline. LATE tends to move more slowly than typical Alzheimer's. Patients with pure LATE often have years — sometimes more than half a decade — of relatively isolated memory impairment without significant decline in other cognitive domains. In my resident clinic, when a family tells me their loved one has been "slowly slipping for years" but is otherwise still managing reasonably well, that indolent course is a meaningful clinical signal and clue to me.

What is spared. Classic Alzheimer's is what we call a multi-domain syndrome — it erodes memory, language, executive function, and visuospatial skills, often in a relatively predictable sequence. LATE tends to spare these other domains, at least early on. The person with LATE can still organize a meal, still follow a conversation, still navigate a familiar neighborhood. Their memory is the primary casualty.

What the MRI shows. Both diseases cause hippocampal atrophy, but in LATE, the shrinkage of the hippocampus is often disproportionate — more severe than you would expect for the patient's overall level of cognitive impairment. When I see a mildly symptomatic patient whose hippocampus looks as though it has been through a decade of severe disease, that mismatch tells me something important.

The Complication: When LATE and Alzheimer's Coexist

Here is where the clinical picture becomes significantly more complex, and where families need to understand that the brain does not always choose just one diagnosis.

LATE co-occurs with Alzheimer's neuropathologic changes in a large proportion of older patients. Among 85-year-olds with advanced Alzheimer's pathology, roughly half also carry significant TDP-43 changes. And when both are present simultaneously, the combined effect is not additive — it is multiplicative. Patients with both LATE and Alzheimer's pathology show substantially more rapid cognitive decline, more severe hippocampal atrophy, worse performance across nearly every domain of neuropsychological testing, and a higher likelihood of presenting as moderately or severely impaired from the very beginning.

This matters enormously in the current treatment landscape. The new anti-amyloid therapies — Leqembi and Kisunla — are precision tools designed to target Alzheimer's biology specifically. For a patient with pure LATE, these medications offer no theoretical benefit and carry real risks. For a patient with both LATE and Alzheimer's, the picture is more complex still: we are currently uncertain whether the presence of significant TDP-43 pathology alters the expected benefits of clearing amyloid. These are not abstract academic questions. They are the questions that will determine whether a real patient in a real clinic room should or should not be placed on a medication that requires monthly infusions and carries a meaningful risk of brain swelling.

Why Doesn't My Doctor Know About This?

I want to be direct here, because this question comes up and it deserves a straight answer.

LATE was only formally named and characterized as a distinct pathologic entity in 2019. The clinical diagnostic criteria proposed by Wolk and colleagues were published just this past year. For most of the last several decades, TDP-43 pathology in elderly patients was either missed entirely or folded into an Alzheimer's diagnosis by default — in part because no biomarker existed to separate them, and in part because the cognitive profile overlaps so substantially.

A 2023 study from the Cleveland Clinic found that patients who were ultimately confirmed to have pure LATE pathology at autopsy were far more likely to have been classified as "cognitively normal" at their initial clinical visit than patients with Alzheimer's. Nearly 42% of LATE patients were initially told nothing was wrong. That is not a failure of individual clinicians; it is a reflection of how genuinely difficult this diagnosis is to make — and how new the tools for making it are.

What This Means for Your Family Right Now

The practical implications of LATE are still evolving, but there are several things worth knowing as you navigate memory care for an older loved one.

Age matters as a clue, not a verdict. If a loved one is in their mid-eighties or beyond and has had a slowly progressive, primarily amnestic syndrome without significant involvement of other thinking skills, LATE is a legitimate part of the differential diagnosis that deserves discussion with their neurologist.

Biomarker testing is increasingly relevant. The primary way to distinguish LATE from Alzheimer's during a patient's lifetime right now is to test for Alzheimer's biology and find it absent. A negative amyloid PET scan, negative CSF amyloid markers, or a negative blood-based p-tau217 test in the right clinical context can shift the diagnosis meaningfully toward LATE. This is not a test ordered routinely, but in the era of disease-modifying therapies, it is increasingly worth asking about.

The treatment conversation is different. A diagnosis that leans toward LATE rather than Alzheimer's changes the risk-benefit calculus for anti-amyloid immunotherapies significantly. Families should feel empowered to have this conversation explicitly with the treating neurologist before any treatment decisions are made.

The pace is usually slower. For families dealing with a pure LATE diagnosis, the trajectory, while still progressive, tends to be more gradual than classic Alzheimer's. That is meaningful information for long-term care planning, financial decisions, and quality of life.

Takeaways

LATE is common and underdiagnosed. Affecting roughly one-third of individuals over 85, it is the second most common neurodegenerative disease in the very old — and most families (and many physicians) have never heard of it.

It mimics Alzheimer's but moves differently. A slower, more isolated memory syndrome beginning after age 75–80, with disproportionate hippocampal atrophy and preserved function in other cognitive domains, should prompt consideration of LATE.

Coexisting LATE and Alzheimer's accelerates decline. When both pathologies are present, the combined burden is more severe than either disease alone — and it complicates decisions about anti-amyloid therapy.

Diagnosis during life requires ruling out Alzheimer's. Until a TDP-43–specific biomarker is validated, the most reliable path to a probable LATE diagnosis is demonstrating the absence of Alzheimer's pathology through amyloid and tau testing.

The field is moving fast. Clinical criteria were only proposed this year. TDP-43–specific PET tracers and blood biomarkers are in active development. This is a diagnosis that will become far more visible — and far more actionable — in the next several years.

Citations and References

Wolk DA, Nelson PT, Apostolova L, et al. Clinical criteria for limbic-predominant age-related TDP-43 encephalopathy. Alzheimer's & Dementia. 2025;21:e14202. https://doi.org/10.1002/alz.14202

Butler Pagnotti RM, Pudumjee SB, Cross CL, Miller JB. Cognitive and clinical characteristics of patients with limbic-predominant age-related TDP-43 encephalopathy. Neurology. 2023;100:e2027–e2035. https://doi.org/10.1212/WNL.0000000000207159

Nelson PT, Dickson DW, Trojanowski JQ, et al. Limbic-predominant age-related TDP-43 encephalopathy (LATE): consensus working group report. Brain. 2019;142(6):1503–1527. https://doi.org/10.1093/brain/awz099