Monoclonal gammopathy of undetermined significance (MGUS) is defined by the presence of a monoclonal protein (M-protein) produced by a small B-cell/plasma cell clone in persons without features of symptomatic disease related to malignant disorders, such as multiple myeloma (MM), Waldenström macroglobulinemia (WM), AL amyloidosis, or other lymphoproliferative disorder [1,2]. Here, MYOM2 is linked to lymphoproliferative syndrome.