Dr. Nick Medford’s patient had plenty of reasons to be terrified of a simple blood test.

His body had shrunk down to a fraction of its size, or so he believed, and the physicians looming over him were enormous. Then there was the needle about to pierce his vein: to the patient’s eye, it was larger than his entire arm.

It might sound like something out of Alice in Wonderland. But this patient’s story belonged to a different genre entirely. Horror, namely. As far as the patient was concerned, there was no point in taking his blood. It was no longer human. Neither was he.

Medford ’s patient was suffering from clinical lycanthropy, defined as the delusional belief that one is turning into a werewolf.…