PPP1CB and plasma cell myeloma: Background: Monoclonal protein (MP) presents in various monoclonal gammopathies, ranging from benign conditions such as monoclonal gammopathy of undetermined significance (MGUS) to life-threatening conditions such as lymphoplasmacytic malignancies (LPMs), which include multiple myeloma (MM) and Waldenström macroglobulinemia (WM).