Generally, genetics is not the problem. Genetic lesions merely set up the problem for metabolic or genetic manipulations.
- Any mutation with 100% fatality in utero.
2. Any non-fatal mutation with 100% penetrance by birth.
Possible exceptions: 2nd site mutations that counteract the first – these fetuses may survive and even show no penetrance until late in life, yet the problem was genetic and the solution was also genetic, a second site mutation. Also, when there are alternative expressed genes: sickle cell anemia never will have 100% penetrance by birth because newborns are expressing fetal hemoglobin, which does not have the sickling mutation.
Why are these cases exceptional? Because gestation is a great laboratory – it is hard to think of a diet, a supplement, a regimen of supplements, and a lifestyle that has not be explored. If there were a metabolic work around for a truly genetic problem, one would think someone would have stumbled upon it and someone would have observed it. Perhaps someone will observe it.