ANSWER: D

MGRS was introduced to acknowledge a clonal plasma cell or B lymphocyte proliferation causing a renal lesion in the absence of hematologic malignancy or other myeloma-defining events; the renal lesion is a consequence of the MIg, which carries major implications for management and prognosis, including the potential for progressive renal injury and ESRD.

MGRS caused by PC is defined as <10% bone marrow plasma cells (BMPCs), <3 g/dl of M protein, and the presence of renal lesions without any other myeloma-defining events (CRAB features; clonal PC ≥60%; serum FLC ratio of ≥100; or >1 focal lesion on magnetic resonance imaging)

References:

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Hogan JJ, Weiss BM. Bridging the divide: An Onco-Nephrologic Approach to the Monoclonal Gammopathies of Renal Significance. Clin J Am Soc Nephrol 11:1681-91, 2016

Fermand J-P, Bridoux F, Kyle RA, et al. International Kidney and Monoclonal Gammopathy Research Group: How I Treat Monoclonal Gammopathy of Renal Significance (MGRS). Blood 122: 3583–3590, 2013.

Bridoux F, Leung N, Hutchison CA, et al. International Kidney and Monoclonal Gammopathy Research Group: Diagnosis of Monoclonal Gammopathy of Renal Significance. Kidney Int 87: 698–711, 2015.

Sethi S, Zand L, Leung N, Smith RJH, Jevremonic D, Herrmann SS, et al. Membranoproliferative Glomerulonephritis Secondary to Monoclonal Gammopathy. Clin J Am Soc Nephrol 5: 770–782, 2010.

Leung N, Bridoux F, Hutchison CA, et al. International Kidney and Monoclonal Gammopathy Research Group: Monoclonal Gammopathy of Renal Significance: When MGUS is No Longer Undetermined or Insignificant. Blood 120: 4292–4295, 2012.