When a man presented to hospital with an enlarging dark lesion on his left thumb, ED doctors bet the farm on a zoonotic origin.

The 45-year-old reported that he had been in direct contact with sheep and handled meat on a farm three weeks earlier.

The lesion had initially manifested as a targetoid papule seven days later (see panel A) and then had begun to grow without any associated pain or sensory deficits (see panel B).

On examination, doctors noted an oedematous dusky nodule on the dorsal surface of the thumb, which was unroofed (see panel C). Bacterial, mycobacterial and fungal cultures were all negative.