Doctors at Prince of Wales Hospital in Hong Kong were at a loss after examining an 84-year-old man admitted for complications relating to an enlarged prostate. But medical experts weren’t perplexed by his prostate issues—they were surprised at the patient’s unnaturally silver skin, fingernails, and even whites of his eyes.

A blood test made clear what the problem was: the concentration of silver in his serum was 423 nmol/L, over 40 times the reference level for a normal result, which is less than 10 nmol/L. The man was diagnosed with a rare case of generalized argyria,