hi michelle. my son has a defect with intron 2G, which IS one of the common 10. on the lab print out that i received with it, it states "Given 90% sensitivity for mutation detection, one would expect that no mutations would be identified in 10% of heterozygous carriers of CAH. Similarly, 18% of those affected by CAH should have a detectable mutation on either parental chromosome. Since genetic variation and other problems can affect the accuracy of direct mutation detection, test results should always be interpreted in light of clinical and family data." i guess that echoes what everyone in the above posts have said. hope this helps.....

louise