The Coffee Shop Origins of Factor V Leiden – ISTH
International Society on Thrombosis and Haemostasis (ISTH) shared a post on LinkedIn:
“Read our full profile on Frits Rosendaal, the 2026 ISTH Grant Medal recipient, and learn more about his life, including this anecdote:
How did they decide on the name Factor V Leiden for the mutation?
Rosendaal recalled the memory with a smile.’We were all gathered in the hospital coffee shop in the lobby. This was at a time when you were still allowed to drink beer and smoke in a hospital, so we were sitting there enjoying a drink and discussing how we should publicize it,’ he said.
Naming conventions for variant proteins often followed geography, typically the hometown of the first identified patient.
But in this case, there was no single ‘first patient,’ as the mutation had been identified through group studies.
So the team improvised with a bit of humor.
They joked that the first patient could have come from a nearby Dutch town but decided the international community might struggle with the pronunciation.
Instead, they chose a simpler, more recognizable name tied to their own institution:
Factor V Leiden, a name that ultimately stuck and became standard worldwide.

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