A rare case of IgE kappa monoclonal gammopathy of undetermined significance identified in a Swedish female

Figures & data

Figure 1. Serum protein electrophoresis. Two electropherograms from the patient, before (March 2016, grey) and at the time of diagnosis (May 2020, black). The peak in the beta-2 fraction observed in May 2020 corresponds to an IgE kappa monoclonal protein co-migrating with the C3 fraction (arrow).

Figure 2. Serum immunofixation. (A) Serum immunofixation against immunoglobulin heavy chains gamma, alpha, mu and immunoglobulin light chains kappa and lambda, showing a band positive for kappa chains (arrow). (B) Serum immunofixation including antisera directed against immunoglobulin heavy chains delta and epsilon. The pattern corresponds to an IgE kappa monoclonal protein (arrows). ELP: serum protein electrophoresis; G: Ig heavy chain gamma; A: Ig heavy chain alpha; M: Ig heavy chain mu; D: Ig heavy chain delta; E: Ig heavy chain epsilon; K: Ig light chain kappa; L: Ig light chain lambda.

Table 1. Results of routine laboratory testing at admission.

	Result	Reference range	Instrument
Hemoglobin	121 g/L	117–153 g/L	Sysmex XN-10, Sysmex Corporation, Kobe, Japan
Creatinine^a	55 µmol/L	45–90 µmol/L	Cobas 8000, Roche Diagnostics, Rotkreuz, Switzerland
Calcium	2.25 mmol/L	2.15–2.50 mmol/L	Cobas 8000, Roche Diagnostics
Albumin^b	42 g/L	36–45 g/L	Cobas 8000, Roche Diagnostics
β2 microglobulin	1.49 mg/L	1.09–2.53 mg/L	BN ProSpec System, Siemens Healthineers, Erlangen, Germany
Lactate dehydrogenase	2.4 μkat/L	1.8–3.4 μkat/L	Cobas 8000, Roche Diagnostics
IgG	10.4 g/L	6.70–14.5 g/L	Cobas 8000, Roche Diagnostics
IgA	1.31 g/L	0.88–4.50 g/L	Cobas 8000, Roche Diagnostics
IgM	0.54 g/L	0.27–2.10 g/L	Cobas 8000, Roche Diagnostics

The results show concentrations in blood (hemoglobin), plasma (creatinine and calcium) and serum (albumin, β2 microglobulin, lactate dehydrogenase, IgG, IgA and IgM).

^aenzymatic method; ^bimmunochemical method.

Table 2. Levels of the serum IgE kappa monoclonal protein and serum free light chains over time.

	06-05-2020	11-06-2020	04-08-2020	13-10-2020	11-01-2021	Reference range
Monoclonal protein (g/L, estimated)	3.6^a	2.4^a	2.5^a	2.4^a	2.8^a	N/A
Kappa FLC (mg/L)	204^a	224^a	220^a /374^a,b	199^a	212^a	6.7–22.4/3.0–19.0^b
Lambda FLC (mg/L)	15.3	16.3	16.7/12.0^b	13.6	15.6	8.3–27.0/6.0–26.0^b
Kappa/lambda FLC ratio	13.3^a	13.7^a	13.2^a /32.0^a,b	14.6^a	13.6^a	0.31–1.56/0.30–1.70^b

A persisting peak in the electropherograms corresponding to the IgE kappa monoclonal protein was evident during regular follow-up. Levels of the monoclonal protein were estimated by relating the area under the curve (AUC) of the monoclonal peak to the AUC of the albumin peak. Serum kappa free light chains were consistently elevated, resulting in an abnormal kappa/lambda free light chain ratio. ^aabnormal result; ^bmeasured using the Freelite assay (Binding Site).

N/A: not applicable; FLC: serum free light chains