Table 1. Definitions of plasma cell related disorders (adopted from Rajkumar et al., ³ ).

Title	Definition
MGUS	Serum monoclonal protein (non-IgM type) <30 g/l
	Clonal bone marrow plasma cells <10%
	Absence of end-organ damage such as hypercalcaemia, renal insufficiency, anaemia, and bone lesions (CRAB) or amyloidosis that can be attributed to the plasma cell proliferative disorder
SMM	Both criteria must be met:
	• Serum monoclonal protein (IgG or IgA) ⩾30 g/l or urinary monoclonal protein ⩾500 mg per 24 h and/or clonal bone marrow plasma cells 10–60%
	• Absence of myeloma defining events or amyloidosis
MM	Clonal bone marrow plasma cells ⩾10% or biopsy-proven bony or extramedullary plasmacytoma
	Evidence of any of myeloma defining events
PCL	Presence of >20% of clonal plasma cells in peripheral blood and/or the absolute number of circulating plasma cells exceeding 2 × 109/l in peripheral blood
Solitary	Biopsy-proven solitary lesion of bone or soft tissue with evidence of clonal plasma cells
Plasmacytoma	Normal bone marrow with no evidence of clonal plasma cells
	Normal skeletal survey and MRI (or CT) of spine and pelvis (except for the primary solitary lesion)
	Absence of end-organ damage such as hypercalcaemia, renal insufficiency, anaemia, or bone lesions (CRAB) that can be attributed to a lymphoplasma cell proliferative disorder
Light-chain	Abnormal FLC ratio (<0·26 or >1·65)
MGUS	Increased level of the appropriate involved light chain (increased κ FLC in patients with ratio >1·65 and increased λ FLC in patients with ratio <0·26)
	No immunoglobulin heavy chain expression on immunofixation
	Absence of end-organ damage such as hypercalcaemia, renal insufficiency, anaemia, and bone lesions (CRAB) or amyloidosis that can be attributed to the plasma cell proliferative disorder
	Clonal bone marrow plasma cells <10%
	Urinary monoclonal protein <500 mg/24 h
AL	Presence of an amyloid-related systemic syndrome (eg, renal, liver, heart, gastrointestinal tract, or peripheral nerve involvement)
	Positive amyloid staining by Congo red in any tissue (eg, fat aspirate, bone marrow, or organ biopsy)
	Evidence that amyloid is light-chain-related established by direct examination of the amyloid using mass spectrometry-based proteomic analysis, or immunoelectronmicroscopy
	Evidence of a monoclonal plasma cell proliferative disorder (serum or urine monoclonal protein, abnormal free light-chain ratio, or clonal plasma cells in the bone marrow)
IgM-MGUS	Serum IgM monoclonal protein <30 g/l
	Bone marrow lymphoplasmacytic infiltration <10%
	No evidence of anemia, constitutional symptoms, hyperviscosity, lymphadenopathy, hepatosplenomegaly or other end-organ damage that can be attributed to the underlying lymphoproliferative disorder
Smoldering WM	Presence of serum IgM monoclonal protein
	Bone marrow lymphoplasmacytic infiltration >10%
	No evidence of anaemia, constitutional symptoms, hyperviscosity, lymphadenopathy, hepatosplenomegaly, or other end-organ damage that can be attributed to the underlying lymphoproliferative disorder
WM	Presence of serum IgM monoclonal protein
	Bone marrow lymphoplasmacytic infiltration >10%
	Evidence of anaemia, constitutional symptoms, hyperviscosity, lymphadenopathy, hepatosplenomegaly, or other end-organ damage that can be attributed to the underlying lymphoproliferative disorder
POEMS	Polyneuropathy
Syndrome	Monoclonal plasma cell proliferative disorder (almost always λ)
	Any one of the following three other major criteria:
	• Sclerotic bone lesions
	• Castleman’s disease
	• Elevated levels of VEGFA
	Any one of the following six minor criteria:
	• Organomegaly (splenomegaly, hepatomegaly, or lymphadenopathy)
	• Extravascular volume overload (oedema, pleural eff usion, or ascites)
	• Endocrinopathy (adrenal, thyroid, pituitary, gonadal, parathyroid, pancreatic)
	• Skin changes (hyperpigmentation, hypertrichosis, glomeruloid haemangiomata, plethora, acrocyanosis, flushing, white nails)
	• Papilloedema
	• Thrombocytosis/polycythaemia