The BSE benchmark Sensex declined by 90 points to 21,165 in early trade today as funds and retail investors indulged in booking profits amid a weak trend in Asian markets. Similarly, the National Stock Exchange index Nifty fell by 28 points to 6,305.Among other Asian markets, Japan's Nikkei was down 0.65 per cent, while Hong Kong's Hang Seng shed 0.48 per cent in early trade.The US Dow Jones Industrial Average ended 0.33 per cent lower in yesterday's trade.