Increased concentrations of the phosphorylated tau protein (pTau) in the blood, which are considered an early indication of Alzheimer’s, also occur in two rare systemic amyloidoses, according to new findings. This has been discovered by researchers from the German Center for Neurodegenerative Diseases (DZNE) and the Hertie Institute for Clinical Brain Research (HIH) at the University of Tübingen. The results are based on blood samples from 280 elderly people from Germany, Italy and the Netherlands and were published in the journal “Nature Medicine” on March 10, 2026.

Transthyretin amyloidosis and immunoglobulin light chain amyloidosis – the two most common forms of systemic amyloidosis – are affected. In these diseases, defective proteins (amyloids) are mainly deposited in the heart and kidneys, not in the brain as in Alzheimer’s. Nevertheless, the blood tests of those affected also showed significantly increased pTau levels.

The scientists emphasize that pTau in the blood is therefore not a specific marker for Alzheimer’s. The finding opens up new diagnostic possibilities: pTau can be determined comparatively easily and inexpensively in the blood and can help to detect systemic amyloidosis earlier or to clarify suspected cases in a targeted manner.

The results also have consequences for Alzheimer’s diagnostics. An elevated pTau level alone is not clear evidence of Alzheimer’s – especially in early stages without cognitive impairment. A reliable diagnosis always requires several examinations and data sources; pTau should not be used as an isolated criterion.

In addition, the marker could be useful in distinguishing polyneuropathies (PNP). This nerve damage with tingling and numbness in the hands and feet can be caused by systemic amyloidosis, but it also has other possible causes. An elevated pTau value can help to distinguish amyloidosis-related PNP from other forms.

The researchers suspect that the pTau increase represents a general stress reaction of the cells to amyloid deposits – regardless of the organ affected. Similar mechanisms have been observed in hibernating animals as a temporary protective mechanism. pTau could therefore be a widespread response of the body to certain pathological stimuli.

The study underlines the need to interpret biomarkers in a differentiated way and to cooperate more closely in the diagnosis of neurodegenerative and systemic diseases.

Original Paper:

Blood phosphorylated tau elevation in immunoglobulin light chain and transthyretin amyloidosis; Stephan A. Kaeser, Stephanie A. Schultz, Anna Hofmann et al.; Nature Medicine (2026); DOI: 10.1038/s41591-026-04272-2

Editor: X-Press Journalistenbüro GbR

Gender Notice. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple naming and gendered designations are used for better readability. ected.