Is Odour a Possible Diagnostic Tool for Parkinson's Disease?
Specific musky scent in sebum is linked to current and future diagnoses of Parkinson's Disease.
Parkinson's Disease (PD) is a degenerative disease associated with the death of dopaminergic neurons, leading to debilitating symptoms such as tremors, muscle rigidity, and sleep disturbances. There is currently no cure for PD, and diagnoses are often made after significant motor control has already been lost.
One "Super-Smeller" is reportedly able to identify early PD through the identification of a specific musky odour. Joy Milne first noticed this scent on her husband 12 years before he was eventually diagnosed with PD. She later noticed the smell on members of a PD support group she attended with her husband. Upon being tested, Milne was able to identify PD patients from healthy controls using only her sense of smell. She recognized one healthy control as a Parkinson's patient, who ended up developing the disease years later.
As this scent is not identifiable by most individuals, researchers at the University of Manchester have teamed up with Milne to discover metabolites that are responsible for this odour. The aim of this study was to create a modified test that could potentially be used by professionals in the diagnosis of PD.
PD Patients were swabbed on their upper backs to collect sebum samples which were then analyzed using a dynamic headspace and gas chromatography coupled to mass spectrometry method, allowing for the identification of four metabolites that likely contribute to the difference in sebum scent that occurs between patients and healthy controls: eicosane, hippuric acid, octadecanal, and perillic aldehyde. No significant difference was found between Parkinson's Disease patients who were taking medication compared to those who were not. Combinations of the potential metabolites were also evaluated by the super-smeller for similiarity to the native PD smell.
Increased concentrations of these metabolites in the sebum of PD patients may be due to increased sebum production, which would allow for better retention of the metabolites on the skin. Changes in skin microflora may play a role, as PD patients tend to have higher levels of Malassezia spp. on their skin which increases lipase activity. This may contribute to an increase in lipophilic molecules such as eicosane, perillic aldehyde, and octadecanal.
The researchers' future directions for this study are to use a larger sample size to validate volatile biomarkers as a predictor of PD.
"A larger study with extended olfactory data from human smellers as well as canine smellers in addition to headspace analyses is the next step in further characterizing the PD sebum volatilome. This will enable the establishment of a panel of volatile biomarkers associated with PD and will open new avenues for stratification as well as facilitate earlier detection of PD and further the understanding of disease mechanisms."