Vitiligo does not have "a gene" — it's polygenic: dozens of genes each nudge risk slightly, alongside real environmental/immune triggers this project documents elsewhere. There is no single Punnett square for "will my child have vitiligo." What follows is two honest, separate things: (1) standard transmission genetics for one risk variant at a time, which is real and exact, and (2) the actual population-level numbers that matter for the disease as a whole, which come from published family/twin studies, not from multiplying single-gene odds together.