Hughes Syndrome is a form of thrombosis, as quoted by Google;
'The antiphospholipid syndrome (APS) is the association of thrombosis or recurrent pregnancy loss with persistent antiphospholipid antibodies.'

Essentially, tldr; blood clotting which can result in miscarriage, cardiovascular issues and early-stroke.
It is not passed via a parent, but it does appear to be a hereditary disorder; meaning it is likely passed on from an ancestor who had it.

Suggestions for a game mechanic involving this condition
- Mutation is simply named 'Thrombosis'
- Mutation is revealed at birth
- Male and females can have it, however males would have no related breeding affects
- Mutation would cause a random chance of spontaneous miscarriage at some time within 3-day pregnancy, resulting in the same affect as a CRB, with a higher chance of mutation to off-set the breeding loss (likely the same pass-rate of a GMO cow).
- Females cannot hunt due to cardiovascular/clotting event risk.
- Earlier death (perhaps 10 years rather than 15 years)
- This mutation would not be passed by the parent, however if your lion has this mutation within the last three generations, there is a chance the mutation will spontaneously appear in their offspring.
- No special lineart necessary, just like DU's.

This is a very rough, loose idea for now - any suggestions and comments are welcome :)