PA H11 | Plasma Cell Dyscrasias (Multiple Myeloma) — Glossary

Deposition of amyloid fibrils derived from monoclonal immunoglobulin light chains (particularly λ type) in organs such as kidney, heart, liver, nerves, and tongue; a serious complication of myeloma and MGUS.

Free monoclonal light chains (κ or λ) excreted in urine in plasma cell dyscrasias; they precipitate at 40–60°C and redissolve at 100°C, and are NOT detected by standard urine dipstick.

The commonest renal lesion in myeloma ('myeloma kidney'); free light chains precipitate with Tamm-Horsfall protein in distal tubules, forming obstructive casts that cause tubular atrophy and renal failure.

The four myeloma-defining end-organ damage features: HyperCalcaemia, Renal failure, Anaemia, and Bone lytic lesions; presence of at least one is required (with plasma cell and M-protein criteria) to diagnose myeloma.

An abnormal plasma cell morphology seen particularly in IgA-secreting myeloma, with a fiery red cytoplasmic fringe due to accumulation of IgA paraprotein within the cell.

Suppression of normal (non-clonal) immunoglobulin production in myeloma, caused by clonal plasma cell crowding and cytokine-mediated inhibition; predisposes to recurrent bacterial infections, especially encapsulated organisms.

A more sensitive electrophoretic technique that uses class-specific antibodies to identify the heavy-chain class and light-chain type of an M-protein; required to characterise a monoclonal band seen on SPEP.

The principal growth and survival cytokine for myeloma cells, produced in an autocrine/paracrine loop between myeloma and marrow stromal cells; drives clonal expansion and resistance to apoptosis.

The tall, narrow, sharply demarcated peak on serum protein electrophoresis representing a monoclonal immunoglobulin; its position (γ or β-γ region) helps identify the immunoglobulin class.

A pre-malignant condition with M-protein present but marrow plasma cells <10% and no CRAB end-organ damage; carries ~1% annual risk of progression to myeloma; requires observation, not treatment.

A structurally identical immunoglobulin or immunoglobulin fragment produced by a single clone of plasma cells, appearing as a narrow M-spike on serum protein electrophoresis.

Plasma cells containing multiple grape-like cytoplasmic inclusions (Russell bodies) of condensed immunoglobulin; a histological marker of intense immunoglobulin production, seen in myeloma and some reactive states.

A malignant neoplasm of clonal plasma cells proliferating in the bone marrow and producing a monoclonal immunoglobulin (M-protein), associated with CRAB end-organ damage.

A broad, diffuse elevation of the gamma globulin region on SPEP reflecting a non-clonal increase in immunoglobulins from multiple plasma cell clones; occurs in chronic infections, autoimmune disease, and liver cirrhosis — contrasts with the narrow M-spike of myeloma.

Characteristic radiological appearance of myeloma bone disease on plain X-ray: round, well-defined osteolytic defects with no surrounding sclerotic rim, most conspicuous in the skull ('pepper-pot skull'), vertebrae, and pelvis.

A cytokine produced by myeloma and stromal cells that activates osteoclasts, causing the purely lytic bone destruction characteristic of myeloma; also inhibits osteoblasts via DKK-1.

A serum biochemistry finding in myeloma where the albumin-to-globulin ratio falls below 1 (normal ~2:1) due to excessive M-protein elevating the globulin fraction while inflammation and nutritional depletion lower albumin.

The stacking of red blood cells in coin-roll chains due to coating by elevated serum proteins (M-protein), seen on blood film in myeloma and other high-protein states; drives a markedly elevated ESR.

A gel-based technique that separates serum proteins by electrical charge into albumin and α1, α2, β, γ globulin fractions; used to detect the monoclonal M-spike of plasma cell dyscrasias.

A lymphoplasmacytic lymphoma secreting a monoclonal IgM paraprotein; characterised by hyperviscosity syndrome (IgM pentamers) and lymphoplasmacytic marrow infiltrate, with absence of lytic bone lesions.

A small protein shed by plasma cells into the serum; elevated levels reflect myeloma tumour burden and impaired renal clearance, and are the cornerstone of the ISS (International Staging System) for myeloma prognosis.