Low-secretory multiple myeloma

Abstract

Multiple myeloma (MM) is an incurable malignancy arising from postgerminal B lymphocytes. It is estimated to account for 10-15% of haematological malignancies and 1% of all malignancies. Non-secretory multiple myeloma (NSMM) is a rare variant of MM, where no monoclonal immunoglobulin (M-protein) can be demonstrated in either the urine or serum. NSMM is estimated to occur in 1-5% of all myeloma cases. So-called 'low-secretory' forms also exist, where the degree of immunoglobulin production does not fulfil the diagnostic criteria, but monoclonal production does occur. The lack of M-protein in NSMM may be due to the inability of the plasma cell to excrete the immunoglobulin, an inherent low synthetic capacity, or intra- or extra-cellular degradation of the M-protein upon production. Patients typically present with fatigue, bone pain and recurrent infections. Bone involvement is common in this disorder with an estimated 80% of patients having radiographic abnormalities upon diagnosis. The majority present with focal lytic lesions (~60%), with osteoporosis (~20%), pathological fractures (~20%) and spinal compression fractures (~20%) seen in the remainder. Metastatic disease is a significant contributor to patient morbidity, since it significantly affects the patient's ability to perform activities of daily living. The humerus is the second-most common site affected after the femur. Surgical intervention is aimed at providing pain relief and restoration of limb function, and is usually not indicated in patients with a very short life expectancy, but this practice remains controversial. In this report we describe a patient with a low-secreting myeloma, presenting with a pathological fracture, in which establishment of the diagnosis according to the World Health Organization (WHO) criteria required crative sampling.