Happens in a lot of types of fish... but personally I haven't seen it as I only pay attention to catfish... there are a few RedTail Cats around with it as well if you search them on the site
Here in Brazil, Shovelnose cats are raise as food in large fish farms, but platinum morphs are rare. But it happens, regular shovelnose turn into platinums after a few months. But sometimes they turn to regular colors again. There are no garantees that a platinum shovelnose keep that color for life, that´s what the guy from a fishfarm told me that. He sold one platinum for a Public Aquarium and advised them against that.....after 1 year the cat turn to the regular colours lol
its similar to vitiligo in humans, where their skin turns white, loss of black pigments or all pigments in parts or all of their skin, like Michael Jackson. Its not like albino which they're born with the genetic defect of missing black pigments. Sometimes this vitiligo, or xanthic as pet owners call it, can revert back to normal coloration. Pretty neat nonetheless.
update...
That's one nice lookin tsn.
Congrat's. I also have a piebald tsn. His color has changed back and forth over the last couple years. He's been getting his color back little by little lately. I hope he end's up casper white like yours!!!