Can an employer refuse to hire me on the basis of genetic testing that revealed I am at higher risk to develop a rare disease?
No. Title II of the Genetic Information Nondiscrimination Act of 2008 (GINA), is a federal law which prohibits genetic information discrimination in employment.
If your employer requires genetic testing, or appears to be discriminating against you on the basis of a genetic test, you may want to consult with a local attorney.