Causes
| Cause | Details |
|---|
| Waldenstrรถm macroglobulinemia | #1 cause. IgM paraprotein -large pentamer is most viscous. Symptoms at IgM > 3 g/dL. |
| Multiple myeloma | Less common (IgA > IgG -IgA polymerizes). ~2โ5% of MM cases. |
| Leukostasis | WBC > 100K (AML) or > 200โ300K (CLL/ALL). White cell plugging in microvasculature. |
| Polycythemia vera | Hct > 60โ65%. RBC sludging. |
Classic Triad
- Mucosal bleeding -epistaxis, gingival bleeding (paraprotein interferes with platelet function and clotting factors)
- Visual changes -blurred vision, "sausage-link" retinal veins on fundoscopy, retinal hemorrhages
- Neurologic symptoms -headache, confusion, dizziness, stroke, coma
Do NOT transfuse pRBCs before plasmapheresis in paraprotein hyperviscosity -adding RBCs to already viscous blood will worsen sludging and can precipitate stroke or MI.
Pathophysiology
Excess paraprotein (most commonly IgM) increases serum viscosity, leading to sludging of blood in the microvasculature. This causes hypoperfusion and end-organ damage affecting the brain, eyes, and mucosal surfaces. IgM is the most common cause because it exists as a pentamer (~900 kDa) -five immunoglobulin subunits linked together -making it far larger than IgG (~150 kDa) or IgA (~160 kDa monomer). Even modest concentrations of IgM dramatically increase viscosity. IgA can also cause hyperviscosity because it tends to polymerize, but this is less common. IgG rarely causes hyperviscosity because it remains a small monomer. The relationship between immunoglobulin concentration and viscosity is exponential, not linear -small increases in paraprotein at high levels cause disproportionate rises in viscosity. Additionally, paraproteins interfere with platelet aggregation and clotting factor function, contributing to the bleeding diathesis.
Clinical Triad -Detailed Findings
| Category | Specific Findings | Mechanism |
|---|
| Mucosal Bleeding | Epistaxis (most common), gingival bleeding, GI bleeding, menorrhagia, purpura | Paraprotein coats platelets (impaired aggregation) and interferes with fibrin polymerization and clotting factors |
| Visual Changes | Blurred vision, diplopia, visual loss. Fundoscopy: "sausage-link" retinal veins (alternating dilated/constricted segments), Roth spots, retinal hemorrhages (flame-shaped), papilledema, cotton-wool spots | Hyperviscous blood distends retinal veins and causes stasis โ retinal ischemia and hemorrhage |
| Neurologic Symptoms | Headache, dizziness, vertigo, confusion, somnolence, obtundation, hearing loss, ataxia, stroke, coma | Cerebral hypoperfusion from sludging in cerebral microvasculature; can progress to frank infarction |
Diagnostic Workup
| Test | Expected Finding | Significance |
|---|
| Serum viscosity | Normal: 1.4โ1.8 cP. Symptomatic: > 4 cP. Emergency: > 5โ6 cP | Definitive measurement. Must be ordered specifically (not part of routine labs). |
| SPEP / Immunofixation | M-spike on electrophoresis; immunofixation identifies isotype (IgM, IgA, IgG) | Identifies the paraprotein. Large M-spike correlates with viscosity. |
| UPEP (24-hr urine) | Bence Jones protein (free light chains) | Supports myeloma diagnosis; assesses renal light-chain burden. |
| Quantitative immunoglobulins | Markedly elevated IgM (> 3 g/dL) in Waldenstrรถm; elevated IgA or IgG in myeloma | IgM > 3 g/dL almost always causes symptoms. Other Ig levels may be suppressed. |
| Fundoscopic exam | "Sausage-link" retinal veins, Roth spots, flame hemorrhages, papilledema | Pathognomonic findings. Should be performed on ALL suspected cases. Findings resolve after plasmapheresis. |
| CBC with peripheral smear | Rouleaux formation (RBCs stacked like coins), anemia, possible leukocytosis | Rouleaux is classic. Anemia may be dilutional or from marrow infiltration. |
| Coagulation studies | Prolonged PT/PTT, prolonged thrombin time | Paraprotein interferes with clotting factors and fibrin polymerization. |
| BMP, LDH, uric acid | Elevated LDH, elevated uric acid, possible renal insufficiency | Assess for tumor lysis risk and end-organ damage. |
Mnemonic -VISCOUS (Hyperviscosity Syndrome):
Vision changes (blurred vision, "sausage-link" veins, Roth spots) ยท Immunoglobulin (IgM most common -pentamer) ยท Sludging of blood (hypoperfusion, microvasculature) ยท Coagulopathy / bleeding (epistaxis, mucosal, platelet dysfunction) ยท Obtundation / neuro symptoms (headache, confusion, coma) ยท Underlying cause (Waldenstrรถm #1, myeloma, leukostasis) ยท Serum viscosity > 4 cP (emergency > 5โ6 cP)
Clinical Examples
๐ Case 1, Waldenstrรถm with Epistaxis and Visual Changes
Patient: 68M with known Waldenstrรถm macroglobulinemia presents with recurrent epistaxis and blurred vision over the past 3 days. On exam, bilateral retinal hemorrhages and "sausage-link" retinal veins on fundoscopy.
Labs: Serum viscosity 8.2 cP (markedly elevated). IgM 5.8 g/dL. CBC shows rouleaux formation. Hgb 9.2.
Action:
- Emergent plasmapheresis -viscosity 8.2 is critically elevated. Do NOT wait for heme/onc consult to initiate.
- Aggressive IV NS -hydration to reduce viscosity while awaiting pheresis.
- Do NOT transfuse pRBCs -will worsen sludging at this viscosity level.
- Serial fundoscopic exams after pheresis to confirm resolution of retinal findings.
- After viscosity controlled, discuss initiation of rituximab-based chemotherapy with heme/onc.
๐ Case 2, Multiple Myeloma (IgA) with Confusion
Patient: 72F with IgA multiple myeloma on lenalidomide presents with progressive confusion and severe headache over 24 hours. Family reports increasing somnolence.
Labs: Serum viscosity 5.1 cP. IgA 6.2 g/dL (polymerized). BMP shows Cr 2.1 (baseline 1.0). Peripheral smear shows rouleaux.
Action:
- Plasmapheresis -symptomatic hyperviscosity with neurologic findings. IgA less commonly causes hyperviscosity than IgM, but this patient's IgA is polymerizing.
- Neuro checks q1h -monitor for progression to obtundation or coma.
- CT head -rule out intracranial hemorrhage or stroke as alternative/concurrent diagnosis.
- Discuss chemotherapy adjustment with heme/onc -current regimen not controlling disease.
- Monitor renal function -Cr elevation may be from hyperviscosity-related renal hypoperfusion or light-chain nephropathy.
๐ Case 3, New Waldenstrรถm with DVT and Hyperviscosity
Patient: 55M presents with left leg DVT and is incidentally found to have IgM 4.5 g/dL on workup. Reports fatigue and "haziness" in vision for weeks. Fundoscopy shows early sausage-link changes. Serum viscosity 4.8 cP.
Action:
- New diagnosis of Waldenstrรถm macroglobulinemia with symptomatic hyperviscosity. Bone marrow biopsy for confirmation.
- Plasmapheresis -symptomatic with visual changes and viscosity 4.8 cP.
- Anticoagulation for DVT -heparin drip (monitor closely given bleeding risk from paraprotein).
- Avoid pRBC transfusion before viscosity is reduced -even if Hgb is low, transfusion can precipitate stroke/MI.
- Rituximab-based therapy (e.g., bendamustine-rituximab or ibrutinib) for definitive treatment. Note: rituximab can cause transient "IgM flare" (paradoxical IgM rise) -pheresis may need to be repeated.