While the days of lacking health insurance due to a pre-existing condition may be over, people with serious health conditions will still have to pay plenty for treatment under most health plans under Obamacare's exchanges.

Consulting firm Avalere Health reviewed public exchange coverage rates for 11 rare-disease treatment drugs. In its report, published in the Journal of Managed Care & Specialty Pharmacy, it found that about two-thirds of exchange plans cover the drugs. But because coverage varies widely among these plans, Avalere cautioned consumers with such health conditions that they should carefully review plans to see how much they will actually be liable for during treatment for a rare disease.

The amount of coverage varied widely by plan medal. Avalere considered only bronze and silver plans in 15 states in the study. Drugs included in the analysis were those that treat Huntington disease, hydatidosis, parathyroid carcinoma, atypical hemolytic uremic syndrome, sickle cell anemia, advanced soft tissue sarcoma, and Gaucher disease type 1.