there was even an episode of house where the cause was gold poisoning.

I'm pretty sure it was silver, not gold.

It gives a person a "gray/purple" skin color that makes them look dead. See: https://en.wikipedia.org/wiki/Argyria

That doesn't necessarily mean that the element is poisonous per se. Many good/healthy substances are poisonous at high levels,e.g.: Vitamin A poisoning [0] Water poisoning [1]

[0] https://en.m.wikipedia.org/wiki/Hypervitaminosis_A [1] https://en.m.wikipedia.org/wiki/Water_intoxication