Cook County Sheriff Tom Dart said seven suspects were arrested and warrants were issued for three others, including janitor Tijuana Leonard, the Chicago Tribune reports.
Leonard worked the night shift for an office-cleaning service.
Investigators said the ring stole data from as many as 250 patients' files from offices at a Northwestern University physicians' group, and then used the information to charge more than $300,00 in ID theft victims received a $5,700 bill from a suburban jewelry store.
Dart said the arrests were the result of a five-month investigation headed by his office, with help from suburban police departments and the U.S Postal Inspection Service.
"It was a simple plot, but it was well thought-out and well-executed," Dart said.