Chapter 21: Multiple Myeloma and Related Plasma Cell Neoplasms

Multiple Myeloma and Related Plasma Cell Neoplasms begins by defining paraproteinaemia as the presence of a monoclonal immunoglobulin band, signifying the abnormal expansion of a single clone of plasma cells. The text details the pathogenesis of these conditions, identifying the neoplastic cell as a post-germinal centre plasma cell that has undergone genetic transformations, such as chromosome 14q translocations and the dysregulation of cyclin D genes. A critical conceptual framework presented is the progression from precursor states, such as monoclonal gammopathy of undetermined significance (MGUS) and smouldering myeloma, into symptomatic disease. Symptomatic multiple myeloma is defined by the CRAB criteria—hypercalcaemia, renal impairment, anaemia, and bone lesions—which reflect the systemic tissue damage caused by malignant cell proliferation and paraprotein secretion. Diagnostic methodologies are extensively covered, including serum protein electrophoresis, free light chain assays, and bone marrow examinations that utilize immunohistochemical staining for CD138. The chapter emphasizes the importance of advanced cross-sectional imaging, such as MRI and PET scans, for detecting skeletal involvement that may be missed by conventional radiography. Furthermore, the management of the disease has been revolutionized by the introduction of proteasome inhibitors and immunomodulatory drugs, often used in triple-therapy combinations followed by autologous stem cell transplantation for eligible candidates. The discussion extends to other plasma cell disorders, including systemic AL amyloidosis, where light chain deposition leads to organ failure, and the rare POEMS syndrome. By examining the intricacies of hyperviscosity syndrome and the role of supportive care, the chapter establishes a comprehensive guide for understanding the diagnosis, risk stratification, and modern therapeutic landscape of haematological malignancies.