Beyond monoclonal gammopathy of undetermined significance, clinical spectrum of immunoglobulin M gammopathy: a case series with focus on the diagnostic and management challenges.

Immunoglobulin M monoclonal gammopathy is detected in Waldenström macroglobulinemia (WM), a rare lymphoplasmacytic lymphoma with serum immunoglobulin M. We report three rare presentations with focus on diagnostic and management challenges of type I cryoglobulinemia, type II cryoglobulinemia, and Bing-Neel syndrome. In approximately 10% of WM cases, macroglobulins can precipitate to cryoglobulins. Type I and II cryoglobulinemia, representing 10-15% and 50-60% of WM cases, respectively, present with vasculitis and renal failure. Bing-Neel syndrome, representing 1% of WM patients, is a rare neurological complication with lymphoplasmacytic infiltration in the brain. WM diagnosis includes bone marrow biopsy, immunophenotypic analysis, and MYD88 L265P mutation. We initiated management of cryoglobulinemia with dexamethasone, rituximab, and cyclophosphamide; in Bing-Neel, bortezomib and dexamethasone, followed by a Bruton tyrosine kinase inhibitor.