> I'd worry that this was somehow acquired rather than just random. If it is exceedingly rare, I always worry it isn't a coincidence but rather a yet not understood method of transmission.

Bad luck is bad luck--not everything has a controllable cause. 70% of all zygotes spontaneously abort.

The difference is that we would leave such children to die a century ago.

I don't know what the modern answer is for children with these kinds of debilitating errors in their DNA.