I love making TS realistic, but personally, I do not want to go as far as having real diseases such as these in my game.
They're serious real-life issues, not a fun game feature.
And I'm sure a majority of people (including myself) may even find it offensive to have them in TS4, especially those who've experienced such things or have watched others go through it, and are ones who escape to the game to get away from those things.
We can easily save everyone the trouble and use our imaginations if we want to take our gameplay that far.