Table 1. Diagnostic criteria of plasma cell dyscrasia.

The table synthesized the most recent diagnostic criteria for plasma cell dyscrasia according to the International Myeloma Working Group.

	M spike		BM		CRAB#	Comments
MGUS	< 3 g/dL	AND	< 10%	AND	Absent	Diagnosis requires exclusion of other lymphoproliferative diseases
SMM	≥ 3 g/dL	OR	≥ 10%	AND	Absent
MM	Any concentration on SPEP/UPEP	AND	Any % or presence of plasmacytoma	AND	Present	Truly non secretory MM is an exception as an M spike can not be identified on SPEP, UPEP or FLC
PC Leukemia^	Absent/Present	AND	Absent/Present	AND	Absent/Present	Defined by the presence of peripheral blood circulating clonal PC > 2×109/L or 20% of leukocytes
Solitary Plasmacytoma	Absent§	AND	Absent	AND	Absent	Defined as a single site of abnormal PC proliferation in the bone (osseous) or soft tissue (extraosseous)

^#: Hypercalcemia is defined as total serum calcium higher than 11.5 mg/dL; renal insufficiency is defined by a serum creatinine exceeding 2 mg/dL or estimated glomerular filtration rate less than 40 ml/min; anemia is defined by hemoglobin less than 10 g/dL or less than 2 g/dL the normal reference values; bone lesions include lytic lesions, pathologic fractures or severely osteopenic bone disease. Hyperviscosity, recurrent infections related to hypogammaglobulinemia and amyloidosis represent evidence of end organ damage as well.

^{^}: PC leukemia is further classified into primary when occurring de novo, or secondary, when it represents the leukemic phase of MM.

^§: a small M spike can be occasionally seen.

Abbreviations: M, monoclonal; BM, bone marrow invasion by monoclonal malignant plasma cells; CRAB, hypercalcemia, renal failure, anemia, bone lesions; MGUS, monoclonal gammopathy of undetermined significance; SMM, smoldering multiple myeloma; MM, multiple myeloma; PC, plasma cell; SPEP, serum protein electrophoresis; UPEP, urine protein electrophoresis; FLC, free light chain.