The Sims 4 has added vitiligo in a free update
A new update for The Sims 4 has added options to give characters vitiligo, the autoimmune disorder which causes patches of skin to lose pigmentation. Rather than a handful of preset full-body patterns, The Sims 4's vitiligo impressively comes as loads of patterns for separate bodyparts, so you can create a wide range of effects. And no, you don't need to buy an expansion for it.