* Futures down: Dow 71 pts, S&P 9 pts, Nasdaq 54 pts
By Tanya Agrawal
July 22 (Reuters) - U.S. stock index futures fell on Wednesday as corporate earnings disappointed, especially from Apple, the world's largest company.
* Apple shares slumped 6.2 percent to $122.61 in premarket trading, a day after the iPhone maker's revenue forecast for the fourth quarter fell below expectations.
* Disappointing earnings from other technology giants such as Microsoft and Yahoo also added to losses.
* Microsoft fell 3.9 percent to $45.45 after reporting its biggest quarterly loss, as the company wrote down its Nokia phone business and demand fell for its Windows operating system.
* Yahoo was down 2.2 percent at $38.85 after it forecast lower-than-expected revenue for the current quarter as it struggles to revive its core online advertising business.
* U.S. stocks had closed lower on Tuesday as results from IBM and United Technologies dampened early optimism over earnings season.
* While markets are near record highs, June-quarter earnings of S&P 500 companies are expected to dip 1.9 percent, according to Thomson Reuters data, well below the 5.9 percent gain forecast on Jan. 1.
* Adding to the weakness, commodities resumed their downward spiral with gold and oil prices under pressure.
* Dow components Coca Cola and Boeing are scheduled to report before the bell and American Express results are expected after the close.
* Data expected on Wednesday includes existing home sales data. Home sales, which reached a 5-1/2-year high in May, are expected to have risen 1.2 percent at an annual rate of 5.40 million units in June. The data is expected at 10 a.m. ET (1400 GMT).
* GoPro rose 2.9 percent to $63.90 after the action camera maker reported a better-than-expected quarterly profit and forecast current-quarter revenue above market estimates, helped by strong sales in Asia.
Futures snapshot at 7:16 a.m. ET:
* S&P 500 e-minis were down 8.75 points, or 0.41 percent, with 92,578 contracts traded.
* Nasdaq 100 e-minis were down 54 points, or 1.16 percent, on volume of 18,672 contracts.
* Dow e-minis were down 71 points, or 0.4 percent, with 9,709 contracts changing hands. (Editing by Don Sebastian)