Clinical features and presentation

• Renal involvement is the predominant feature in 33% with nephrotic syndrome (oedema, fatigue and lethargy) ± renal impairment (usually mild).

• Cardiac symptoms predominate in 20-30%: CCF due to restrictive cardiomyopathy notably with right sided features (4 JVP, peripheral oedema and hepatomegaly).

• Peripheral neuropathy occurs in 20%; 10-15% present with isolated neuropathic symptoms; typically painful sensory polyneuropathy; carpal tunnel syndrome in 40%; autonomic neuropathy may cause postural hypotension, impotence and disturbed GI motility.

• GI involvement may be focal or diffuse: malabsorption, perforation, haemorrhage and obstruction may occur; hepatomegaly 25%; macroglossia 10%.

• Haemorrhage occurs at some time in up to 33% of patients; usually non-thrombocytopenic purpura, often periorbital causing characteristic 'raccoon eyes' appearance.

• Vocal cord infiltration may cause dysphonia; large joint arthropathy; adrenal and thyroid infiltration may cause endocrine dysfunction; cutaneous plaques and nodules usually on face or upper trunk; pulmonary infiltration rarely symptomatic.

Investigation and diagnosis

• High index of suspicion required; consider in patient with nephrotic syndrome, cardiomyopathy, peripheral neuropathy, hepatomegaly or autonomic neuropathy.

• Confirm diagnosis by histological examination of biopsy of affected organ or subcutaneous fat aspirate, rectal biopsy or labial salivary gland biopsy stained with Congo Red for red-green birefringence under polarised light; confirm AL amyloidosis by immunochemistry for k or l light chains (50% are negative).

• Assess severity of organ involvement:

- FBC: 5 Hb suggests probable myeloma.

- Serum chemistry: to assess renal and hepatic function.

- |32-microglobulin: prognostic indicator in MM (see p276).

- Coagulation screen; may be a coagulopathy due to absorption of factor X and sometimes FIX by the amyloid.

- Serum protein electrophoresis, immunofixation and densitometry: to detect, type and quantitate any paraprotein present (~70%; usually only modest quantity).

- Serum immunoglobulins: to identify immuneparesis (suggests MM).

- Serum free light chain assay: useful in patients with no detectable paraprotein in serum or urine (10-15%).

- Creatinine clearance and 24h quantitative proteinuria: to assess renal dysfunction.

- Urine electrophoresis: to detect, type and quantify paraprotein (85%; 90% have albuminuria).

- BM aspirate and trephine biopsy: usually only mild 4 in % plasma cells; overt MM in 20%.

- Skeletal survey: if MM suspected.

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