Alzheimer's disease dominates how we talk about dementia, but it is far from the only disease that can cause memory loss. One lesser-known condition, called limbic-predominant age-related TDP-43 encephalopathy, or LATE, may independently account for 15 to 20 percent of dementia cases.
LATE occurs when a protein called TDP-43 accumulates in brain cells, eventually damaging and killing them. The disease affects many of the same regions as Alzheimer's, including the hippocampus, amygdala, and parts of the temporal and frontal lobes. As a result, the two conditions can look remarkably similar. Both may cause memory loss, difficulty finding words, and problems holding information in mind.
This overlap creates a major diagnostic challenge. LATE can currently be confirmed only through an autopsy, although clinicians may suspect it when a patient has Alzheimer's-like symptoms but tests negative for Alzheimer's biomarkers. The conditions can also coexist. Around 40 percent of people with dementia show at least some LATE pathology, often alongside Alzheimer's disease or vascular damage.
This has important implications for dementia research and policy. If clinical trials group together patients whose symptoms arise from different underlying diseases, researchers may underestimate whether a treatment works for the specific pathology it was designed to target. It also becomes harder for patients and families to receive an accurate explanation of what is happening.
Investment in biomarkers for LATE, more representative dementia research, and diagnostic guidelines that account for mixed pathologies could help move dementia care beyond a one-disease model. Alzheimer's remains the most common cause of dementia, but treating every case of memory loss as Alzheimer's risks overlooking a substantial part of the problem.