Well, some comp authors (their books would mention their agents in the Acknowledgment sections) are:
Lisa Genova (Still Alice is about early-onselt Alzheimers and maybe her second book is too?)
Michelle Wildgen (You're Not You is about Lou Gehrig's/ALS)
Jodi Picoult (approximately five gazillion books, many of which are medical issues related, such as My Sister's Keeper)
Jennifer Haigh (The Condition is about some kind of inherited disease)
Joseph Monninger (Eternal on the Water is about Huntington's -- his agent is/was Christina Hogrebe)
If you do Amazon checks for any of those, they would likely lead you to "You might also like" results, and you could amass quite a list of comp titles and check all those agents.
Good luck!!