Discovery of DOPA Decarboxylase as a High-Specificity Biomarker for Parkinson’s Disease

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Summary of  Nature Medicine https://doi.org/10.1038/s41591-026-04212-0 
Dr. Katharina Bolsewig  et al.

Points

Researchers identified that the protein DOPA decarboxylase is significantly elevated in the cerebrospinal fluid of patients with Parkinson’s disease and dementia with Lewy bodies compared to healthy controls.
The international study utilized two newly developed highly sensitive immunoassays to demonstrate that DDC levels are up to two and a half times higher in patients with synucleinopathies.
Statistical analysis confirmed the biomarker is highly specific for Lewy body disorders with area under the curve values exceeding zero point nine for differentiating them from Alzheimer’s disease.
Autopsy data revealed a direct correlation between elevated DDC concentrations and the progression of alpha-synuclein pathology in the brain tissue of deceased patients with confirmed Lewy body dementia.
This discovery provides neurologists with a much-needed objective tool to ensure accurate diagnosis at early stages and avoid the risks associated with improper treatment for other dementia types.

Summary

The clinical utility of DOPA decarboxylase (DDC) as a quantitative cerebrospinal fluid (CSF) biomarker for the differential diagnosis of Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Given the symptomatic overlap between DLB and other neurodegenerative conditions like Alzheimer’s disease (AD), current diagnostic protocols frequently result in misdiagnosis. The research sought to determine if elevated CSF DDC concentrations could serve as a specific objective tool to distinguish synucleinopathies from both healthy controls and AD cohorts.The consortium developed two highly sensitive immunoassays and validated them across multiple cohorts, including 740 patients in clinical groups and 78 autopsy-confirmed cases. Results demonstrated that CSF DDC levels were significantly elevated in DLB and PD, showing up to a 2.5-fold increase compared to controls and a 1.9-fold increase compared to AD patients. The biomarker exhibited high diagnostic accuracy with area under the curve (AUC) values exceeding 0.9. Furthermore, immunohistochemistry confirmed the colocalization of DDC and $\alpha$-synuclein in the substantia nigra, while elevated CSF levels correlated directly with progressing $\alpha$-synuclein pathology in autopsy-confirmed DLB.The findings suggest that DDC is a biologically relevant biomarker that reflects the presence of motor impairment and underlying pathological changes in the brain. While the elevated concentration was linked to the presence of motor symptoms, it did not correlate with their severity, suggesting DDC is a marker of disease state rather than progression. This quantitative measurement provides clinicians with an objective tool to avoid harmful treatments resulting from misdiagnosis. The researchers emphasize that while these immunoassays pave the way for clinical implementation, further standardization is required to integrate this test into routine neurological care.

Link to the article: https://www.nature.com/articles/s41591-026-04212-0

References

Bolsewig, K., Bellomo, G., Hok-A-Hin, Y. S., Al Idrissi, I., Vermunt, L., Lleó, A., Alcolea, D., Sieben, A., Engelborghs, S., Simonsen, A. H., Hasselbalch, S. G., Bech, S., Morrema, T. H. J., Hoozemans, J. J. M., Bol, J. G. J. M., van Alphen, J., Gaetani, L., Chiasserini, D., Paolini Paoletti, F., … Teunissen, C. E. (2026). A quantitative DOPA decarboxylase biomarker for diagnosis in Lewy body disorders. Nature Medicine, 32(3), 1073–1084. https://doi.org/10.1038/s41591-026-04212-0