Wang W, et al. - The validity of flow cytometry as a supplemental method to diagnose immunoglobulin D (IgD) multiple myeloma (MM) (by detecting the heavy chain of cytoplasmic IgD) was tested. From patients with MM, including five with IgD MM, bone marrow (BM) samples were collected. Each patient’s BM sample was analyzed for antibodies to four types of heavy chains of immunoglobulin (e.g., IgA, IgG, IgM, and IgD) using flow cytometry. Based on the findings, it was concluded that, by enabling cytoplasmic IgD detection, flow cytometry affords a convenient, sensitive and supplemental method to diagnose IgD MM.