Investigation and diagnosis

• FBC and film: normochromic normocytic anaemia 80% (often spuriously low due to increased plasma volume); rarely lymphocytosis or pancytopenia; blood film shows rouleaux or agglutination (cold agglutinins ~5%); may contain circulating lymphoplasmacytic cells.

• ESR/plasma viscosity: 4 in almost all patients (~70% PV >1.8cP), often markedly (ESR commonly >100mm/h); risk of hyperviscosity symptoms when PV >4cP (5-10% at diagnosis); most have symptoms when PV >6cP; PV often correlates well for symptoms in an individual though not between patients.

• Biochemistry: renal impairment unusual; LFTs may be abnormal in advanced disease or cryoglobulinaemia; uric acid may be 4.

• Serum immunoglobulins: 4 IgM; may be mild immuneparesis of IgG (60%) and IgA (20%).

• Serum protein electrophoresis, immunofixation and densitometry: confirms and quantifies IgM paraprotein.

• Urine electrophoresis: scanty Bence Jones protein present in ~50%.

• BM aspirate: often hypocellular; may show infiltration by lymphoplas-macytic cells of variable degrees of differentiation; mast cells may be increased.

• BM trephine biopsy—essential—usually hypercellular; demonstrates intertrabecular infiltrate (diffuse, interstitial or nodular) of lymphoplas-macytic cells (Note: paratrabecular infiltrate suggests follicular NHL); immunochemistry demonstrates light chain restriction.

• BM immunophenotyping: useful in differentiating WM from other B-cell disorders; characteristically pan B-cell marker (CD19, CD20, CD22, CD79) positive (cf myeloma plasma cells); light chain restricted surface IgM; CD10 negative (cf. FL), CD23 negative (cf. CLL); 5-20% express CD5 (must differentiate from CLL and MCL); CD103 and CD138 rarely positive.

• Cytogenetics: no disease defining abnormality described; many normal; presence of IgH translocations (l4q) suggests myeloma.

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