Ross is an active 75-year-old retiree who complains that most of his toenails and his left thumb nail have become discoloured and loose in the past few weeks.

Test your clinical know-how by taking the quiz below. If you select the wrong answer, have another go — you can try as many times as you like!

Emeritus Professor Max Kamien is a senior honorary research fellow, University of WA.

Courtesy Emeritus Professor Max Kamien