Lycanthropy!

The condition of the title can be recognized, Johannes Actuarius tells us in his 1340 Therapeutike Methodos, by examining a person and discovering ulcerated feet and legs from nighttime hours spent wandering among tombs.

As recounted in Ask the Past, the afflicted person makes such wanderings as a wolf before returning in the morning in human form. Actuarius describes the condition as a "melancholy," which means something different to him than it does to us, but in any event the people suffering from the condition often remain silent and sad. All the same, one shouldn't try to comfort them in their wolfish form, as no amount of offered treats and "Oh, sad doggie!" are likely to curb their lupine appetite for, ah, fresh food.

Strangely, no mention is made of the clothing worn by sufferers. The snazzy dressing that makes survivors interested in the werewolf's tailor was apparently a later development.