1. plasma cells >15% in bone marrow with abnormal plasma cells (myeloma cells) or tissue biopsy confirmed plasmacytoma. 2. large amounts of monoclonal immunoglobulin (M protein) in serum: IgG > 35g/L; IgA > 20g/L; IgD > 2.Og/L; IgE > 2.0g/L; IgM > 15g/L or monoclonal immunoglobulin light chain in urine (this week protein) >1.0g/24 hours. In a few cases, bi- or tri-clonality may be present. Xing Wenhua, Department of Cervical Spine Surgery, Second Affiliated Hospital of Inner Mongolia Medical University 3. No other causes of osteolytic lesions or extensive osteoporosis.
To diagnose IgM-type MM, in addition to meeting items 1 and 2, typical MM clinical manifestations and multi-site osteolytic lesions must also be present. Those with only 1 and 3 items are non-secretory MM and need to be further identified as non-synthetic or synthetic but non-secretory subtypes. For those with only items 1 and 2 (especially those without primary and juvenile plasma cells in the bone marrow), reactive plasmacytosis and monoclonal immunoglobulin of undetermined significance (MGUS) must be excluded.