A rare case of the IgE prozone phenomenon in IgE multiple myeloma

IgE multiple myeloma is a rare subtype of myeloma, accounting for <0.1% of all myeloma cases. Difficulties in diagnosing and monitoring this rare myeloma type are recognized, including the need of heightened awareness for initial diagnosis, performing a reflex immunofixation test using an anti-IgE antisera, and recognizing the possibility of the prozone phenomenon. Here, we report a rare case of IgE multiple myeloma with the prozone phenomenon. This case was characterized by a paradoxical increase in IgE levels with a progressive increase in the dilution factor. Moreover, serial monitoring of IgE levels correlated with the trend in the serum free light chain ratio, especially when the monoclonal protein was no longer detectable. This case highlights the need for laboratory professionals to be vigilant about the occurrence of the prozone phenomenon in IgE multiple myeloma.