In this paper, we propose a distributed network coding (DNC) scheme based on digital fountain rateless LT codes for wireless sensor networks (WSNs), where a group of source nodes communicate with a single destination node through a group of relay nodes in a two-hop fashion. The aim of the proposed scheme is to achieve network coding gains. The relay nodes perform linear combinations by using network coding to form network-coded symbols and send them to the destination node. At the destination, a graph-based, rateless code is formed on the fly. The main contribution of this paper is the derivation of an analytical symbol error rate (SER) bound for the proposed coding scheme.