My husband recently had issues with this from his employer; CAH is a chronic medical condition, which means you are eligible for FMLA.  You will need to have a Physician’s Certification completed by your child’s endo; your employer should have the forms, or you can download a generic form at http://www.opm.gov/oca/fmla

Just FYI, due to the new Hippa laws, you are not required to furnish specifics about your child’s condition to your employer, only that a medical condition does exist.

Hope this helps... best of luck to you.