A new study has found that people with longer ring fingers relative to the index finger are much more likely to have motor neurone disease.
UK researchers measured the finger length of 110 people, including 47 with amyotrophic lateral sclerosis (ALS), the most common form of the disease.
The ratio between the fingers has already been linked to many traits, including sporting prowess and aggression, and is believed to be set in the womb.
Experts believe a longer fourth finger relative to the index finger could be partly determined by how much exposure a baby has to the male hormone testosterone before birth.
Indeed, men often do have slightly longer ring fingers than index fingers, while women often do not.
And experts know that motor neurons need testosterone for survival and repair, and men who are born without the ability to use testosterone in the normal way develop a form of motor neuron degeneration.
However, experts say finger length cannot help screen for ALS and more work is needed.
"This simple, but carefully conducted study raises some interesting questions about how events occurring before birth may increase the risk of developing motor neurone disease later in life," the BBC quoted Dr Brian Dickie of the Motor Neurone Disease Association, as saying.
"But it`s important to remember that exposure to higher testosterone in the womb does not directly cause motor neurone disease," he said.
"Many people with long ring fingers will never develop motor neuron disease as we believe there are numerous genetic and environmental factors that need to coincide in order to trigger the disease," he added.
The finding is published in the Journal of Neurology, Neurosurgery and Psychiatry.