The majority of FOXG1 mutations are de novo, which means it was a spontaneous mutation during the pregnancy, there is no genetic reason, and there is usually a 0.01% chance of re-occurrence. In our group, there are four to five families that have either gonadal mosaicism or an actual genetic carrier of the mutation. If someone is a carrier, the mutation does not affect the carrier, but it is passed on to the child, and they have a roughly one in four chance of having a child with a mutation. Gonadal mosaicism is when the parents are NOT carriers, however, in reproductive organs some of the eggs and sperm contain the mutation, resulting in a child with a FOXG1 mutation.
