J.P. Morgan Chase on Friday revealed it took a huge loss from a trading-related loan to a single client in the fourth quarter.
"Equity markets revenue was flat compared to a strong prior year and included the impact of a mark-to-market loss of $143 million on a margin loan to a single client," the company said in its release.
The bank said its equity markets revenue would have been up 12 percent without the client loss for the quarter.
J.P. Morgan failed to name who the specific client was but said on a call with the media that it was "a syndicated margin loan facility to related parties" of Steinhoff International.
The bank said it was likely that other financial firms had exposure to the same client. Steinhoff is a South African retailer whose shares plunged at the end of last year.
The Financial Times reported the mystery client was Christo Wiese, chairman of Steinhoff. The paper said banks including J.P. Morgan, Bank of America and Citigroup face big losses for lending him money secured against shares in the failing company.
It was also a difficult trading environment for the bank's bond trading business. J.P. Morgan said fixed income markets revenue declined 34 percent year over year driven by "continued low volatility" and "tighter credit spreads."