Yo, this has been my special interest for well over 20 years, pretty much since I saw someone with vitiligo for the first time. It’s been absolutely fantastic to see how it’s changed from something that people used to be ashamed of to something that’s regarded as so beautiful and awesome that people want to have characters with it and those with it proudly show it off instead of trying to cover it however they possibly can. So it goes without saying I utterly ADORE helpful resources like this!
However, one little addendum - more about piebaldism than vitiligo. I’m not sure where OP is getting their sources from regarding “trauma from the mother” as that isn’t exactly how it works. Piebaldism is a genetic mutation, and hereditary. Very strongly inherited, in fact. Just so happens to be rare in humans in comparison to other mammals. (And, btw, it occurs in every known mammal! How neat is that?!) It is an autosomal dominant mutation, which means only one copy of the altered gene in each cell is all that’s needed to cause the disorder. So essentially there is exactly a 50/50 chance of the kid inheriting it if the parent has it.
Trauma during pregnancy can indeed cause genetic mutations so that is a possibility but that isn’t the general, most documented cause.
some handy little factoids on piebaldism:
Because it is a genetic mutation, it does indeed happen before birth and will be present at birth. Piebald patches typically won’t change over time because it is directly related to the mutation of two specific genes and unless you get some crazy CRISPR gene therapy going on, that’ll never ever change. Now that said, it isn’t impossible for changes to happen and re-pigmentation has been documented. Genes are weird, man. Most commonly seen when an injury on a de-pigmented spot heals, mostly because scar tissue behaves a little differently from normal skin, but also because of the specific way piebald mutation works. Essentially the genes that would normally produce melanin have been shut off, but still retain the possibility to turn back on if something somehow changed in the DNA. For the vast majority of cases it stays the same though.
Piebaldism presents most commonly with a de-pigmented triangular spot on the forehead/scalp that leads to a white forelock. Sometimes eyebrows and eyelashes may also be affected. Upwards of 90% of cases have the white forelock at birth.
Another little difference between the patches of piebaldism and vitiligo is that piebald patches tend to have “islands” of regular pigment within the de-pigmented patches, sometimes even hyper-pigmented.
Technically it is possible to have both piebaldism and vitiligo since one is genetic and one is an (presumed) autoimmune response. So do with that what you will for character creation! I’ve used it myself.
Piebaldism is not known to cause vision or hearing problems. however, congenital (aka present at birth) hearing loss and heterochromia are somewhat common with it. Again, genes are weird.
And then one final note for both piebaldism and vitiligo: neither one are 100% either present or not present at birth. Vitiligo can form while still in the womb, although it is very rare and there are only a few cases known. Likewise, piebaldism may not show up until after birth as genes can mutate with age, exposure to radiation, or with particular diseases. I also highly recommend doing research on the patterns of vitiligo as there are a lot of different kinds that are even more broken down than OP’s handy visualization, and they’re all equally fascinating and lovely!