It exists if I understand you correctly. You can TRADE BTC/USD. BTC is crypto USD is FIAT (FOREX). The hottest area this week appears to be crypto ...
source https://www.google.com/url?rct=j&sa=t&url=https://www.quora.com/Is-forex-trading-a-cryptocurrency&ct=ga&cd=CAIyGmM2Nzk3ODA2ZWViNjVjODI6Y29tOmVuOlVT&usg=AFQjCNEhUNv6tspvS_PMxNZkwm4jkVE99g
