Hyperviscosity Syndrome from IgA Multiple Myeloma: A Rare Diagnosis Revealed by Head Trauma

Introduction/Background/Significance: Multiple myeloma is a clonal plasma cell proliferative disorder in which excess production of monoclonal immunoglobulins by plasma cells leads to end-organ damage, most commonly including hypercalcemia, renal dysfunction, anemia, and bone lytic lesions. Less commonly, it can manifest as hyperviscosity syndrome, occurring when excessive levels of proteins increase the serum viscosity, causing downstream hypoperfusion and physical stress on weaker venules. This presents classically with mucosal bleeding, visual changes, and neurologic deficits. In multiple myeloma, symptomatic hyperviscosity typically occurs due to the excessive production of immunoglobulin M (IgM), as it is the largest of the paraproteins. IgA myeloma, which involves overproduction of a smaller paraprotein, is even less likely to cause hyperviscosity syndrome, requiring higher immunoglobulin concentrations to become symptomatic and clinically significant. We present a rare case of IgA multiple myeloma where early recognition and treatment of hyperviscosity syndrome were critical in preventing serious neurologic morbidity.

Materials and Methods/Case Presentation/Objective: A 72-year-old male with a history of cerebrovascular accident on clopidogrel presented with new left sided deficits and lethargy after a fall with head trauma. Initial imaging revealed a right-sided subdural hematoma (SDH), and he underwent emergent burr hole evacuation. Despite surgical intervention, his neurologic deficits persisted, wound dressings continued to saturate with blood despite multiple blood products, and repeat imaging revealed the SDH reaccumulated. Nurses noted difficulty with phlebotomy and described the blood as thick. Hematology was consulted, and laboratory evaluation revealed anemia (Hgb 8.3 g/dL), elevated total protein (11.4 g/dL), globulin (9.3 g/dL), and a markedly elevated serum viscosity of 23.3 cP. A plasma cell profile from six months prior was reviewed and found to be suggestive of IgA lambda monoclonal gammopathy (IgA 3760 mg/dL and lambda light chains 18.98 mg/dL). Plasmapheresis was initiated, resulting in rapid clinical improvement and return to the patient's neurologic baseline. Serum viscosity decreased to 4.0 cP after the first session. Subsequent laboratory findings showed reduction in IgA (2590 mg/dL), total protein (8.5 g/dL), and globulin (4.7 g/dL).

Results/Description/Main Outcome Measures: A bone marrow biopsy confirmed IgA lambda multiple myeloma with 80% plasma cell infiltration and cytogenetic findings of t(11;14) and monosomy 13. The patient stabilized neurologically and began induction therapy with cyclophosphamide, bortezomib, and dexamethasone. Overall, the identification of hyperviscosity syndrome secondary to IgA multiple myeloma as the underlying etiology for the patient's persistent encephalopathy and bleeding led to decisions to proceed with plasmapheresis resulting in clinical improvement and provided a bridge to definitive therapy.

Conclusions: This case shows the importance of considering hyperviscosity syndrome secondary to multiple myeloma as an etiology of persistent encephalopathy and bleeding despite treatment of a subdural hematoma following a head injury. In addition, while IgM is more commonly associated with hyperviscosity, IgA-related cases can present with severe symptoms at high immunoglobulin levels. Finally, it highlights the importance of avoiding delay in treating hyperviscosity syndrome when clinical suspicion is high, as prompt intervention can prevent irreversible complications and promote clinical stabilization.