(A) MALDI-TOF results in normal serum (no monoclonal protein present). The x-axis represents mass/charge ratio. Three separate rows are presented for each heavy chain isotype. (B) MALDI-TOF results after each cycle of daratumumab in a patient with IgG kappa MM. The pathogenic clone and daratumumab have different molecular weights and are therefore easily distinguishable. Reference mass/charge ratios exist for several other moAbs used in treating myeloma that can achieve a serum concentration high enough to cause interference. (C) “Immune reconstitution” (oligoclonal) pattern seen after autologous transplant. Multiple IgG kappa and lambda clones are noted, but the initial pathogenic clone is absent. (D) A monoclonal IgG kappa protein with a glycosylated light chain in an AL amyloidosis patient treated with daratumumab. Glycosylated IgG kappas are up to 12 times more common in patients with AL amyloidosis and are present years before the diagnosis of AL amyloidosis is made.

Used with permission from Dr David Murray.