Is congenital adrenal problem like cah always serious and why?

Not always: Unless it's onset is with birth and associated with severe salt wasting ( that's why it's part of the newborn screen in all 50 states). It's carrier rate is quite common however, almost 1 in 40 so many people ate walking around without knowing they are carriers !

Yes it is: It is serous condition due to deficiency of certain enzymes and needs to be properly diagnosed and treated.