The disease manifestations of MEN2B and Apert syndrome are very different yet, like MEN2B mutations, new Apert syndrome germline mutations also arise at an unexpectedly high frequency (100–1,000 times that expected) at a limited number of nucleotide sites (c.755C>G or c.758C>G), virtually always occur in the male parent and exhibit a paternal age effect (reviewed in [19], [38], [42], [43], [57]). The gene discussed is RET; the disease is Apert syndrome.