Republicans in the Senate released an updated version of the Better Care Reconciliation Act, their plan to overhaul the US healthcare system.

Included in the revised bill is an amendment from Sen. Ted Cruz and Sen. Mike Lee that critics say could make plans with adequate coverage unaffordable to those who have certain medical conditions.

The amendment would allow plans to exist that don't comply with two regulations set up under the Affordable Care Act: community rating and essential health benefits. The latter could have a big impact on preexisting conditions.

So what counts as a preexisting condition that could get you denied coverage under the new plan?

A lot.

A preexisting condition is a term insurance companies used before the ACA, the healthcare law better known as Obamacare, to classify certain diseases or health problems that could cause a person to be denied coverage or make their coverage more expensive than that of people considered healthy.

Before the ACA

The Kaiser Family Foundation estimates that 27% of Americans under 65 have health conditions that could leave them without access to insurance. Some of the pre-existing conditions that insurers declined coverage because of before the ACA, according to the foundation, include diabetes and heart disease, which affects millions of Americans.