ANN ARBOR, MICH. — Lance Bowles knew his son Caden loved cars, but he didn’t realize just how much until the summer when Caden was 6.

“This guy was driving by, and Caden said, ‘Hey, Dad, there’s an Isetta!’ ” Mr. Bowles said, referring to a rather obscure Italian-designed microcar from the 1950s. “The guy turned the car around and said, ‘Did he just call this an Isetta?’ He couldn’t believe it.”

Caden Bowles was, by all accounts, a smart, precocious and joyful boy with extraordinary ardor for automobiles. Though only 11 when he died last fall while awaiting a heart transplant, Caden left an enduring impression on nearly everyone his life touched, including the staff at the University of Michigan C. S. Mott Children’s Hospital here, and Jean Jennings, the well-known automotive journalist who runs the JeanKnowsCars website and is a judge on TruTV’s “Motor City Masters.”

Ms. Jennings’s friendship with Caden resulted in a car show in his honor, held at the hospital last Saturday. Largely unpublicized and closed to the public, Caden’s Car Show was intended to give young patients and their families a diversion from medical ordeals, and to raise awareness for organ and blood donations.