Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Activating mutations in tyrosine kinase receptors KIT or platelet-derived growth factor receptor alpha (PDGFRA) are the main mechanisms causing the disease. Patients generally present with non-specific symptoms, while a number of tumors are discovered incidentally and may be metastatic at the time of diagnosis. Aggressive GISTs have a defined pattern of metastasis to the liver or throughout the abdomen, or both. Though GISTs rarely present systemic or isolated paraneoplastic reactions, a few cases have been reported in the literature. We present the case of a 54-year-old patient with metastatic GIST at diagnosis and the emergence of paraneoplastic manifestations during follow-up.