If you’ve been writing or saying “Irlens Syndrome or Irlen’s Syndrome” you’ve been doing it wrong! Irlen Syndrome was discovered by Helen Irlen in the early 1980s. She named the condition Scotopic Sensitivity Syndrome, but many years later, the condition was renamed after her. In medicine, when they name a disease after the person who discovered it, it’s called an “eponymous disease name.” The medical profession has urged since the 1970s the dropping of the possessive S at the end of disease names which were originally named after their discoverers. The possessive is thought to confuse people by implying that the person named actually had the disease. An ‘apostrophe s’ connotes ownership or possession. Helen Irlen does not have Irlen Syndrome, it was just named after her.
The general public often has a hard time following this rule (let’s call it the no-S rule). Down Syndrome (also spelled without an “s”) is named after John Langdon Down, but the public so often erroneously uses the term, “Downs Syndrome” that many people have concluded the syndrome’s discoverer must have been named “Downs.” He wasn’t.
Other conditions that should always be stated without an “s” are “Munchhausen Syndrome” and “Tourette Syndrome,” but I’m sure we all know lots of people who use the incorrect “Munchhausen’s” or “Tourrette’s Syndrome” instead. And, to make matters worse, many conditions are way more commonly written with an apostrophe “s” than not, making the “s” version seem more correct. This is true for “Alzheimer’s,” “Addison’s,” “Parkinson’s,” “Bright’s,” “Crohn’s,” “Hansen’s,” “Hodgkin’s,” and “Raynaud’s” diseases, all of which usually have the ’s. This just makes the rules even that much more confusing.
The extra “s” also incorrectly finds its way into diseases that aren’t even named after people at all. One such example is Lyme Disease. This disease is named after the town of Lyme, Connecticut (clearly not a person who could have ever suffered from this condition). There should never be an “s” at the end of Lyme Disease, or any other disease named after a place for that matter.
With all that said, regardless of what you do when talking or writing about other conditions (feel free to say and write them however it feels right to you), when it comes to Irlen Syndrome, please leave out the s.
Thanks!