Heavy chain diseases (HCDs) are rare B-cell lymphoproliferative neoplasias characterized by the production of a monoclonal component consisting of a truncated monoclonal Ig heavy chain without the associated light chain. Among them, patients with gamma-HCD are so rare that no more than 150 cases can be found in the literature. In this paper, we report one additional case: an 83-year-old man with a gamma-HCD, in whom a kappa light chain component was detected in the serum by using the serum free light-chain assessment and in addition monoclonal kappa cytoplasmic expression was detected in bone marrow plasma cells by flow cytometric analysis. In the work-up of the patient, the underlying anatomopathological lymphoproliferative disease corresponded to a lymphoplasmacytic lymphoma, as it is stated in the current World Health Organization classification (2008), with both lymphadenopathic and bone marrow infiltration. As in other cases, several autoimmune manifestations (antiphospholipidic syndrome and immune thrombocytopenia) were present during the course of the disease in this patient. This case report illustrates a new case of gamma-HCD, in which serum free light-chain analysis and flow cytometry represented a valuable tool for diagnosis, a finding that could be very important for the future management of these patients.