We study a novel shallow information extraction problem that involves extracting sentences of a given set of topic categories from medical forum data. Given a corpus of medical forum documents, our goal is to extract two related types of sentences that describe a biomedical case (i.e., medical problem descriptions and medical treatment descriptions). Such an extraction task directly generates medical case descriptions that can be useful in many applications. We solve the problem using two popular machine learning methods Support Vector Machines (SVM) and Conditional Random Fields (CRF). We propose novel features to improve the accuracy of extraction. Experiment results show that we can obtain an accuracy of up to 75%.