Puccinia menthae is a rust fungus which galls the leaves of various Mints (Mentha aquatica, etc.), and occasionally Marjoram (Origanum vulgare) or Wild Basil (Clinopodium vulgare) and other species in the Lamiaceae family. Young leaves at shoot tip become thickened, distorted, with purple patches carrying aecia and spermogonia; later uredinia and telia are present.

host

Photograph the rust on the host.  Ensure you have noted the host-plant species in your comments

on plants in the Lamiaceae family, usually recorded on mint (Mentha)