And imagine that because royalty are obligated to marry other royalty, the STI spread throughout the other royal families but didn't spread to the lower classes.
I wonder if in this world this STI would become high status, and therefore be considered attractive.
Bound feet look physically repulsive, but because they were associated with both femininity/daintiness and the upper class, they were eroticized.
I wonder if this STI would be given some fancy name and be sought after rather than avoided.
"Ah yes I have the swollen red flower of the king."