Answer: True

About 5-10% of the patients with monoclonal gammopathy and findings consistent with C3GN by standard IF (on frozen tissue) will actually have a Membranoproliferative GN with masked monoclonal deposits.

These patients require additional IF studies to be performed on protease-digested, paraffin-embedded tissue for identification of the monoclonal immunoglobulin in the deposits.

References:

Leung N, et al. The evaluation of monoclonal gammopathy of renal significance: a consensus report of the International Kidney and Monoclonal Gammopathy Research Group. Nat Rev Nephrol 2019; 15(1): 45-59.

Larsen CP, et al. Membranoproliferative glomerulonephritis with masked monotypic immunoglobulin deposits. Kidney Int 2015; 88(4): 867-873.