The BSE benchmark Sensex gained 87 points in early trade today on the back of covering-up of short positions by participants following monthly expiry in the derivatives segment. The 30-share index moved up by 87 points to 19,504 with realty, healthcare, auto and metal sector stocks leading the rally.Similarly, the wide-based National Stock Exchange index Nifty was up 25 points to 5,931.In Asia, the Hong Kong market gained 0.46 per cent, while Japan's Nikkei Index was up by 1.36 per cent.The US Dow Jones industrial average, however, ended 0.19 per cent lower in yesterday's trade.