When a condition is passed on as a recessive trait (such as with CAH), there is a much greater chance that offspring will inherit the trait if the parents are related.  That is partly why many societies discourage close relatives from marrying...to prevent new generations from passing on genetic diseases and problems. 

Since CAH is a recessive condition and uncommon, it is not unusual that doctors or genetic counselors might "fish" around for information regarding possible close family ties between husband and wife.  (The term they use is “consanguinous.”)  At the same time, this does NOT mean that ALL parents of children with CAH are closely related!

Most people with CAH are “compound heterozygotes” meaning that they’ve inherited DIFFERENT gene mutations from each parent.  If their parents were related, they would more likely be “homozygotes,” meaning they have the SAME gene mutation from both parents.  This suggests that most people with CAH are probably NOT related!  Yes, there are certain populations that have a higher incidence of consanguinity, therefore higher rates of certain types of CAH, but it doesn’t necessarily follow that everyone with CAH is a result of a consanguinous union! 

My CAH son’s father is of German-Swiss-English decent.  I, his mother, am of Chinese decent.  Neither of our ancestors have set foot on each others’ CONTINENTS for many, many generations.  Trust me….we couldn’t be more UN-related!