Parkinson's Disease Diagnosis via Skin Test

A recent study in the journal Movement Disorders suggests that the diagnosis of Parkinson's disease (PD) may now be possible with the help of a skin test. The study results clearly showed the utility of skin tissues for clinical diagnosis of PD through the detection of pathological αSyn.

Parkinson's disease is a neurodegenerative disorder that affects millions of people worldwide. It inflicts significant economic, social, and medical burden on society. Neuropathological changes of PD include deposition of pathological α-synuclein (αSyn) aggregates widely throughout the brain. PD diagnosis is based mostly on clinical signs and can be definitely confirmed upon the postmortem demonstration of substantia nigral αSyn. Misdiagnosis is common, and about 20% of clinically diagnosed PD patients receive an alternative diagnosis postmortem. In this scenario, accurate diagnosis becomes critical.

There is an unmet clinical need in PD to identify biomarkers for diagnosis, preferably in tissues that are peripherally accessible such as skin. Immunohistochemical studies have detected pathological α-synuclein (αSyn) in skin biopsies from PD patients, albeit sensitivity needs to be improved.

Sireesha Manne, Iowa State University, Ames, Iowa, USA, and colleagues provided the ultrasensitive detection of pathological αSyn present in the skin of PD patients, and thus, pathological αSyn in skin could be a potential biomarker for PD.

The researchers used the real‐time quaking‐induced conversion assay for detecting pathological αSyn present in human skin tissues. This ultra‐sensitive and specific assay was optimized for both frozen and formalin‐fixed paraffin‐embedded sections of skin tissue. The seeding kinetics of the αSyn present in the skin from autopsied subjects consisting of frozen skin tissues was determined from 25 PD and 25 controls and formalin‐fixed paraffin‐embedded skin sections from 12 PD and 12 controls.

In a blinded study of skin tissues from autopsied subjects, the researchers correctly identified:

• 24/25 PD and 24/25 controls using frozen skin tissues (96% sensitivity and 96% specificity)
• 9/12 PD and 10/12 controls using formalin‐fixed paraffin‐embedded skin sections (75% sensitivity and 83% specificity)

"Our blinded study results clearly demonstrate the feasibility of using skin tissues for clinical diagnosis of PD by detecting pathological αSyn. Moreover, this peripheral biomarker discovery study may have broader translational value in detecting misfolded proteins in skin samples as a longitudinal progression marker," concluded the authors.

The study, "Blinded RT‐QuIC Analysis of α‐Synuclein Biomarker in Skin Tissue from Parkinson's Disease Patients," was published in the journal Movement Disorders.

DOI: https://onlinelibrary.wiley.com/doi/epdf/10.1002/mds.28242