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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Waldenstrom macroglobulinaemia

Haematology and transfusion · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Symptomatic IgM hyperviscosity

Visual disturbance, mucosal bleeding, headache, confusion, seizure, dyspnoea or heart failure with high IgM requires clinical action before systemic therapy can lower production.

Action: Use ABCDE assessment, obtain fundal examination, FBC, renal, coagulation, IgM and serum viscosity without delaying treatment, avoid non-essential red-cell transfusion and perform urgent therapeutic plasma exchange of about 1–1.5 plasma volumes followed promptly by clone-directed therapy.

Overview

Confirm marrow lymphoplasmacytic lymphoma with an IgM paraprotein, recognise IgM-mediated emergencies and choose symptom-led therapy that avoids hyperviscosity, rituximab-flare and bleeding harm.

WM is lymphoplasmacytic lymphoma involving marrow with an IgM paraprotein. Presentation includes fatigue from anaemia, nodes, splenic fullness, infection or B symptoms, but much morbidity is caused by IgM: hyperviscosity, cold agglutinin haemolysis, cryoglobulinaemia, neuropathy, renal disease and occasional amyloid. Examine nodes, spleen, retina, neurological system, perfusion and bleeding. The IgM concentration correlates imperfectly with viscosity and symptoms; compare each patient with their own baseline and act clinically.

Confirm with marrow aspirate and trephine showing small lymphocytes, plasmacytoid lymphocytes and plasma cells with a clonal B-cell and plasma-cell phenotype. MYD88 L265P is present in most WM and supports classification but is not absolutely specific; wild-type disease needs particularly careful review. CXCR4 mutations can associate with higher IgM and slower BTK-inhibitor response. Exclude IgM myeloma with plasma-cell phenotype, lytic disease and t(11;14), and distinguish marginal-zone lymphoma using splenic, nodal and pathological features.

Practice

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Haematology and transfusionOriginal SBA

Hyperviscosity first action

A patient with known WM develops blurred vision, epistaxis, headache and retinal venous engorgement. IgM is very high and haemoglobin is 82 g/L. What is the most appropriate immediate disease-specific action?

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Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • British Society for Haematology Waldenstrom guidelineUK diagnosis, hyperviscosity, treatment indications and regimen guidance.
  • British Society for Haematology apheresis guidelineUK plasma-exchange practice for symptomatic hyperviscosity.
  • Brukinsa Summary of Product CharacteristicsExact zanubrutinib dose, CYP3A, bleeding and reproductive safety.
  • MabThera Summary of Product CharacteristicsRituximab administration, viral reactivation and infusion safety.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Baseline tests include FBC, film, renal, liver, calcium, LDH, beta-2 microglobulin, quantitative IgM, SPEP, immunofixation, free light chains and immunoglobulins. Test viscosity and examine fundi when symptoms or high IgM raise concern; viscosity measurement must not delay exchange. Use haemolysis, direct antiglobulin, cold agglutinin, cryoglobulin with warm sample handling, neuropathy and anti-MAG tests when indicated. CT stages nodes and spleen; PET is more useful when transformation is suspected.

Observation is first-line for asymptomatic disease regardless of IgM number. Treat symptomatic haemoglobin or platelet compromise, constitutional or bulky disease, hyperviscosity, symptomatic cryoglobulinaemia, cold agglutinin disease, neuropathy, renal disease or amyloid attributable to the clone. Confirm that nonspecific fatigue or neuropathy is actually disease mediated. Use prognostic scores to inform discussion, not as treatment triggers. A slow, low-burden presentation may need a less intensive regimen than rapidly progressive marrow or organ disease.

Symptomatic hyperviscosity needs urgent plasma exchange, generally 1–1.5 calculated plasma volumes with albumin replacement according to the apheresis protocol. One exchange can markedly reduce intravascular IgM, but tissue-to-plasma equilibration and continued production cause rebound. Repeat according to symptoms, fundi, IgM and viscosity while systemic treatment begins. Avoid routine red-cell transfusion until viscosity falls; if severe anaemia threatens oxygen delivery, coordinate small, necessary replacement with exchange and senior assessment.

Systemic selection is individual. Bendamustine–rituximab gives durable disease control but prolonged lymphocyte suppression. Dexamethasone–rituximab–cyclophosphamide is gentler but response may be slower. Zanubrutinib is a continuous BTK inhibitor active across many patients, with response influenced by MYD88 and CXCR4; bleeding, hypertension, atrial arrhythmia, infection and CYP3A interactions matter. Avoid rituximab monotherapy when high IgM creates flare risk. Proteasome-based treatment can act quickly but neuropathy influences choice.

At response, follow symptoms, examination, FBC and IgM trend rather than expecting complete paraprotein disappearance. A biochemical IgM rise alone does not require treatment unless clinical progression follows, but rapid change prompts reassessment. At relapse review remission duration, prior toxicity, mutation context and whether new symptoms are IgM or tumour mediated. Transformation requires biopsy. Support vaccination, infection prevention, neuropathy and cold avoidance and screen for hepatitis B before anti-CD20 therapy.

Key points

  • WM requires an IgM monoclonal gammopathy plus marrow infiltration by lymphoplasmacytic lymphoma; serum IgM concentration alone does not establish the diagnosis.
  • First-line confirmation is marrow aspirate and trephine with morphology, flow and MYD88 L265P testing; assess CXCR4 when it changes BTK-inhibitor expectations.
  • Do not treat an asymptomatic IgM number: indications include symptomatic anaemia or cytopenia, hyperviscosity, bulky disease, B symptoms and clinically important IgM-mediated organ injury.
  • Clinical hyperviscosity is an emergency even if a numerical viscosity threshold is not reached; examine the fundi and arrange urgent plasma exchange.
  • Plasma exchange removes IgM quickly but is temporary; follow with clone-directed therapy or the paraprotein rebounds.
  • Avoid non-essential red-cell transfusion before viscosity is reduced because increased cellular volume can worsen microcirculatory flow.
  • Rituximab can cause an IgM flare, so reduce IgM with plasma exchange or non-rituximab cytoreduction and defer rituximab in high-risk hyperviscosity contexts.
  • First-line options include bendamustine–rituximab, dexamethasone–rituximab–cyclophosphamide and BTK inhibition selected from pace, genetics, neuropathy, cardiac and bleeding risk.
  • Zanubrutinib is given 320 mg daily or 160 mg twice daily and requires bleeding, infection, blood-pressure, rhythm and CYP3A review.
  • Repeat tissue or PET-directed biopsy for sudden focal growth or LDH rise because transformed lymphoma needs an aggressive pathway.

Aetiology

01

Lymphoplasmacytic B-cell clone

WM arises from a mature B-cell clone differentiating toward plasma cells and secreting monoclonal IgM within marrow and sometimes nodes or spleen.

02

MYD88-driven signalling

MYD88 L265P activates NF-kB and BTK pathways in most cases, while CXCR4 mutations modify migration, IgM burden and BTK-inhibitor response.

03

Precursor IgM MGUS

Many cases are preceded by IgM MGUS, but most precursor clones never progress and do not require systemic treatment.

Pathophysiology

  1. 1
    Marrow infiltration

    Lymphocytes, plasmacytoid cells and plasma cells replace marrow and cause anaemia, thrombocytopenia and constitutional or splenic symptoms.

  2. 2
    Intravascular IgM

    Large pentameric IgM remains mainly intravascular, raising viscosity and making plasma exchange rapidly effective at removing the pathogenic protein.

  3. 3
    Autoantibody activity

    Monoclonal IgM can bind nerve myelin, red-cell antigens or cryoprecipitate, producing neuropathy, cold agglutinin haemolysis, cryoglobulinaemia and vascular injury.

  4. 4
    Tissue deposition

    IgM or light chains can cause renal disease and occasional amyloid, while lymphoplasmacytic cells enlarge spleen, liver and nodes.

Clinical features and red flags

Marrow burden

Fatigue, dyspnoea, infection, bruising or bleeding reflects anaemia, thrombocytopenia and immunoparesis from lymphoplasmacytic infiltration.

HyperviscosityRed flag

Visual blur, retinal haemorrhage, mucosal bleeding, headache, vertigo, confusion or dyspnoea requires urgent exchange assessment.

IgM autoantibody disease

Length-dependent neuropathy, cold haemolysis, acrocyanosis, purpura or cryoglobulinaemic renal and skin disease may drive treatment.

Tissue burden

Nodes, splenic discomfort, early satiety, hepatomegaly and constitutional symptoms reflect lymphoma rather than paraprotein alone.

Transformation

Rapid focal growth, marked LDH rise or severe new B symptoms needs PET-directed biopsy for aggressive lymphoma.

Red flags requiring action

  • Retinal haemorrhage or venous engorgement, mucosal bleeding, confusion, ataxia, seizure or heart failure is symptomatic hyperviscosity and requires urgent plasma exchange.
  • Cold-induced acrocyanosis, haemolysis, purpura, renal injury or neuropathy can be IgM-mediated despite modest tumour bulk and may itself indicate treatment.
  • Rapid node growth, disproportionate LDH, severe B symptoms or extranodal mass raises histological transformation and requires urgent PET-directed biopsy.
  • Rituximab can transiently raise IgM; giving it alone to a patient with very high IgM or hyperviscosity can precipitate deterioration.

Investigations

  1. 01
    Reference standard: marrow aspirate and trephineFirst stepReference standard
    Why
    Demonstrate lymphoplasmacytic lymphoma and distinguish plasma-cell and marginal-zone alternatives.
    Interpretation and limitations
    Integrate morphology, B-cell and plasma-cell flow and tissue architecture; quantify involvement and obtain material for MYD88 and selected CXCR4 testing.
  2. 02
    IgM and monoclonal studies
    Why
    Characterise secretory burden and a measurable response marker.
    Interpretation and limitations
    Use quantitative IgM, SPEP, immunofixation and free light chains; IgM concentration alone neither diagnoses WM nor defines treatment need.
  3. 03
    Hyperviscosity assessment
    Why
    Identify a reversible microcirculatory emergency.
    Interpretation and limitations
    Use symptoms, examination and fundoscopy with serum viscosity; do not wait for a result or a universal numerical threshold when the clinical syndrome is present.
  4. 04
    IgM-complication testing
    Why
    Attribute neuropathy, haemolysis, cryoglobulin or renal injury to the clone.
    Interpretation and limitations
    Use DAT, haemolysis, cold titre, correctly handled cryoglobulins, anti-MAG and nerve studies, urine and biopsy as directed; exclude common alternatives.
  5. 05
    CT or transformation PET-CT
    Why
    Stage tissue disease and select a biopsy site when biology changes.
    Interpretation and limitations
    CT assesses nodes and spleen routinely; use PET and adequate biopsy for discordant rapid growth or LDH rather than diagnosing transformation from scan alone.

Differential diagnosis

01

IgM MGUS

A smaller asymptomatic IgM clone with less than 10% marrow lymphoplasmacytic infiltration and no related symptoms is monitored as precursor disease.

02

Marginal-zone lymphoma

Splenic or nodal MZL can secrete IgM and share MYD88 occasionally; morphology, distribution, phenotype and genetics establish the lymphoma entity.

03

IgM myeloma

Rare IgM plasma-cell myeloma has plasma-cell morphology, lytic disease and often t(11;14), not lymphoplasmacytic marrow and typical MYD88 biology.

04

Other hyperviscosity states

IgA myeloma, polyclonal inflammation and extreme cellular counts can impair flow, but symptoms, protein type, viscosity and marrow disease differ.

Management

01IgM monoclonal proteinSeparate precursor, lymphoma and myelomaFirst stepSPEP or immunofixation detects monoclonal IgM.+
  1. 1Assess hyperviscosity, neuropathy, haemolysis, cryoglobulin, renal, nodes, spleen, cytopenia and constitutional symptoms.
  2. 2Perform marrow morphology, flow and MYD88 with CT and selected t(11;14) or plasma-cell studies.
  3. 3Classify IgM MGUS, WM, marginal-zone lymphoma, IgM myeloma or an IgM-related disorder and set observation or treatment.
02HyperviscosityExchange first and suppress productionClinical visual, neurological, bleeding or cardiopulmonary hyperviscosity develops.+
  1. 1Avoid non-essential red cells, obtain fundal and viscosity baseline without delaying treatment and contact apheresis urgently.
  2. 2Exchange about 1–1.5 plasma volumes and repeat according to symptoms and rebound.
  3. 3Begin clone-directed systemic therapy, sequencing rituximab to avoid IgM flare and monitoring IgM and clinical recovery.
03Symptomatic WMChoose regimen by symptom and genotypeMarrow, tumour or IgM-mediated disease creates a clear treatment indication.+
  1. 1Define pace, MYD88 and CXCR4, neuropathy, bleeding, cardiac, infection, renal and reproductive context.
  2. 2Select bendamustine–rituximab, DRC, zanubrutinib or another current BSH regimen with flare prevention.
  3. 3Monitor the clinical driver, counts, IgM and regimen toxicity and stop fixed-duration or continue BTK therapy as specified.
04Abrupt progressionBiopsy for transformationRapid focal growth, high LDH, severe B symptoms or extranodal mass emerges.+
  1. 1Stabilise organ compromise and use PET-CT to select the most discordant accessible lesion.
  2. 2Obtain adequate histology before steroids when physiology permits.
  3. 3Treat confirmed aggressive transformation through the large B-cell pathway using prior exposure and transplant fitness.
Key medicines and prescribing safety4 treatments · regimens, roles and cautions+
First-line rapid treatment for symptomatic IgM hyperviscosity because most IgM is intravascular.

Therapeutic plasma exchange

Exchange approximately 1–1.5 calculated plasma volumes urgently with albumin-based replacement under the apheresis protocol, repeating according to clinical response, fundal findings, IgM and viscosity rebound.

It is temporary and must be followed by clone-directed therapy. Monitor access, haemodynamics, calcium, coagulation and IgM rebound; avoid unnecessary red-cell transfusion before viscosity is reduced.

Fixed-duration first-line or relapse therapy that gives deep durable control in fit patients.

Bendamustine with rituximab

Give bendamustine 90 mg/m² IV on days 1 and 2 with rituximab 375 mg/m² IV day 1 every 28 days for up to six cycles, modifying through the WM protocol and sequencing rituximab when flare risk is high.

Screen hepatitis B, provide prophylaxis where indicated and monitor infusion reaction, IgM flare, prolonged CD4 lymphopenia, infection, cytopenia, renal and skin toxicity. Use Pneumocystis and antiviral prevention according to protocol and avoid pregnancy.

BTK inhibition for symptomatic WM, including a chemotherapy-free continuous option informed by genotype, comorbidity and preference.

Zanubrutinib

Give 320 mg orally once daily or 160 mg orally twice daily continuously until progression or unacceptable toxicity, using SmPC dose reductions with moderate or strong CYP3A inhibitors.

Monitor bleeding, infection, atrial rhythm, blood pressure, cytopenia, liver and skin cancer; interrupt around procedures. Avoid strong CYP3A inducers, review anticoagulants, use effective contraception and stop breastfeeding.

Complications

01

Hyperviscosity

Raised intravascular IgM impairs retinal, cerebral, pulmonary and mucosal microcirculation and can cause irreversible visual or neurological injury.

02

IgM-related organ disease

Anti-MAG neuropathy, cryoglobulinaemia, cold agglutinin haemolysis, renal disease and amyloid can dominate despite limited marrow burden.

03

Marrow and immune failure

Anaemia, thrombocytopenia, immunoparesis and treatment-related suppression cause fatigue, bleeding and clinically significant recurrent bacterial or opportunistic infection.

04

Transformation or secondary malignancy

A minority develops aggressive lymphoma or therapy-related myeloid disease, signalled by abrupt clinical and biological change.

Monitoring and follow-up

  • During observation monitor symptoms, examination, FBC, renal, IgM and immunoglobulins at a risk-appropriate interval without treating the number alone.
  • During hyperviscosity follow clinical neurology, vision, bleeding, fundoscopy, IgM and viscosity rebound and begin systemic control before exchange benefit fades.
  • During anti-CD20 therapy monitor infusion reaction, hepatitis B prophylaxis, IgM flare, immunoglobulin failure, neutropenia and infection.
  • During zanubrutinib review bleeding, anticoagulants, rhythm, blood pressure, infection, FBC, liver, interactions and peri-procedural interruption.
  • At relapse reassess symptom attribution, prior response duration, transformation pattern, MYD88 and CXCR4 relevance and cumulative immune and marrow toxicity.

Special situations

IgM number is not indication

A very high stable IgM can be asymptomatic, while a lower concentration with cryoglobulin or neuropathy can cause major organ disease.

Exchange is unusually efficient

Pentameric IgM is predominantly intravascular, so one plasma-volume procedure can improve symptoms rapidly even though the clone is unchanged.

Rituximab can worsen first

Transient IgM release or redistribution can precipitate hyperviscosity. Sequence treatment and exchange instead of assuming antibody therapy immediately lowers protein.

MYD88 supports not proves

The common mutation strengthens WM diagnosis and predicts BTK biology, but it also occurs in other lymphomas and must be interpreted with marrow morphology.

Neuropathy needs attribution

Diabetes and age-related neuropathy are common. Anti-MAG phenotype, tempo and nerve testing prevent toxic lymphoma treatment for an incidental paraprotein.

Common pitfalls

  1. 01

    Do not diagnose WM from serum IgM without marrow lymphoplasmacytic lymphoma.

  2. 02

    Do not wait for a numerical viscosity result when visual, neurological or bleeding hyperviscosity is clinically present.

  3. 03

    Do not transfuse red cells routinely before exchange in hyperviscosity or use exchange without systemic follow-on treatment.

  4. 04

    Do not give rituximab alone into uncontrolled high-IgM hyperviscosity without a flare-prevention plan.

  5. 05

    Do not treat asymptomatic disease solely because IgM rises gradually.

  6. 06

    Do not call rapid focal growth ordinary WM progression without biopsy for transformation.

A relatively tolerable fixed-duration option for symptomatic WM when a slower response is clinically acceptable.

Dexamethasone–rituximab–cyclophosphamide

A common DRC cycle gives dexamethasone 20 mg IV or orally and rituximab 375 mg/m² IV on day 1 with cyclophosphamide 100 mg/m² orally twice daily on days 1–5, every 21 days for six cycles.

Avoid rituximab-first exposure during uncontrolled hyperviscosity. Screen hepatitis B; monitor infection, cytopenia, glucose, mood, bladder and gonadal toxicity and use contraception. Dose and route must follow the centre protocol.