The woman who can smell Parkinson’s disease

Joy Milne is a 72-year-old retired nurse from Perth, Scotland, who has had an extraordinarily sensitive sense of smell, called hyperosmia, all of her life. In some ways it has been a curse. She can’t tolerate being around people wearing perfume and she has to avoid aisles in the supermarket where chemicals are shelved. Many years ago, when her physician husband was 33, she noticed that he had developed a strange, musky odor.  At first, she thought he just needed to take a shower, but the smell persisted. Six years later, her husband was diagnosed with Parkinson’s disease. As she met other people with Parkinson’s disease, she found that to her they all smelled of the same musky odor. 

In 2012 she met Professor Tilo Kunath, a neuroscientist studying Parkinson’s disease at the University of Edinburgh, and mentioned her ability to identify people with Parkinson’s disease by the odor they emitted. He was skeptical, and they agreed to a blinded test.  He gave her twelve T-shirts, six worn by people with known Parkinson’s disease and six from normal people.  She correctly identified the six with Parkinson’s, but she also smelled the telltale odor in one of the normal controls.  It tuned out that the “normal control” was diagnosed with Parkinson’s disease one year later.

Prof. Kunath was impressed, and he started a collaborative study with Professor Perdita Barran, a chemist at the University of Manchester, in searching for the molecules producing the smell that Joy Milne can detect. Using mass spectrometry, they discovered specific fat molecules in sebum, an oily secretion of the skin, that were present only in people with Parkinson’s disease. They have now developed a skin-swab/mass spectrometry test that appears to have 90% accuracy in identifying people with Parkinson’s disease, and work is underway to see if the test can be used to identify those like Joy Milne’s husband who had pre-symptomatic Parkinson’s.

As we all know, dogs have an extraordinarily powerful ability to smell. It has been estimated that the canine capacity for odor detection is 10,000 to 100,000 times greater than that of humans. This appears to be due to a combination of a greater number of olfactory sensors in the nasal cavities and a much more efficient flow of sniffed air through the nose allowing prolonged evaluation of the odorant. Dogs also have a keen ability to track the source of an odorant making them important partners in many military, law enforcement, and search and rescue operations. Some dogs have been trained to detect the smell of certain cancers as well as diabetes, malaria, and COVID-19. 

Like dogs, Joy Milne’s nose can detect diseases other than Parkinson’s. According to an article in SPIEGEL International, people with tuberculosis smell to her like damp cardboard. Diabetes  smells like nail polish. Cancer smells like mushrooms. And Alzheimer’s disease smells like rye bread. She is collaborating with researchers around the world to see if her special nose can lead to identifying chemical biomarkers of these other diseases, perhaps improving our ability to make early, even pre-symptomatic diagnoses.

The primary source for this post was: Diana Kwon. A supersmeller can detect the scent of Parkinson’s, leading to an experimental test for the illness. Scientific American, October 11, 2022.