Hyperviscosity Syndrome as a Rare Presentation of Immunoglobulin G Kappa Smoldering Multiple Myeloma Successfully Treated With Daratumumab
Year: 2026
Type: article
Study design: Case Report
Abstract: Hyperviscosity syndrome (HVS) is an oncologic emergency most commonly associated with Waldenstrom macroglobulinemia and immunoglobulin (Ig)M paraproteinemia. Clinically, significant HVS in smoldering multiple myeloma (SMM), particularly IgG-associated disease without overt CRAB (hypercalcemia, renal insufficiency, anemia, and bone lesions) criteria, is exceedingly rare. We report a unique case of IgG kappa smoldering myeloma complicated by symptomatic HVS, manifesting with retinal hemorrhage, epistaxis, and gross hematuria, despite the absence of overt end-organ myeloma-defining events. A 70-year-old patient with Sjogren syndrome and longstanding monoclonal gammopathy showed gradual progression from high-risk monoclonal gammopathy of undetermined significance (MGUS) to smoldering myeloma over several years. Bone marrow biopsy showed 10% plasma cells, with no high-risk cytogenetic abnormalities on limited fluorescence in situ hybridization (FISH) testing. Positron emission tomography/computed tomography (PET/CT) imaging repeatedly showed no fluorodeoxyglucose (FDG)-avid osseous disease. In the setting of HVS, serum viscosity peaked at 5.7 centipoise, with concomitant IgG elevation to 5,463 mg/dL and an M-protein of 3.01 g/dL. Given symptomatic hyperviscosity, treatment with daratumumab was initiated despite the absence of SLiM (≥ 60% clonal plasma cells, light chain ratio ≥ 100, and magnetic resonance imaging (MRI) focal lesions)-CRAB criteria for overt multiple myeloma. Following therapy, serum viscosity rapidly improved from 5.7 to 2.2, with corresponding reductions in IgG and M-protein levels and resolution of bleeding manifestations. This case highlights that symptomatic hyperviscosity may occur in IgG smoldering myeloma at a relatively modest plasma cell burden and may itself represent a clinically meaningful indication for early therapeutic intervention.
Source: Journal of Medical Cases
DOI: 10.14740/jmc5398
Institution: Presbyterian Healthcare Services
Language: English
Subfield: Hematology
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7208706925
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