The ACA bars use of pre-existing conditions
The Patient Protection and Affordable Care Act (ACA) prohibits the use of pre-existing conditions—such as heart disease or a cancer diagnosis—to deny, increase premiums, or impose waiting periods for health insurance coverage. Medicaid and Medicare also can't refuse to cover you or charge more because of a pre-existing condition. Prior to the ACA, Americans could be charged higher premiums, denied or dropped from their health insurance due to a pre-existing condition or serious illness such as cancer.
The ACA complements the Genetic Information Nondiscrimination Act (GINA) which prohibits discrimination by most health insurance plans and employers based on genetic information such as an inherited genetic mutation associated with an increased risk of cancer. An inherited mutation such as BRCA or Lynch syndrome cannot be considered a pre-existing condition in regard to health insurance or employment.