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Amyloidosis

 

Definition of amyloidosis

  • Deposition of a normally soluble protein in a tissue that disrupts normal function

 

Types of amyloidosis

There are many different subtypes of amyloid, these are the most clinically relevant:

  • AL [remember ‘L’ for light chain]
    • Light chain deposition in tissues
    • Can occur spontaneously but associated with multiple myeloma and Waldenstrom’s macroglobulinaemia
  • AA [remember ‘A’ for arthritis]
    • Complication of chronic inflammatory conditions (e.g. RA) and chronic infections (TB, osteomyelitis)
    • Deposition of serum amyloid A protein, predominantly in liver, spleen and kidneys
  • Beta-2 microglobulin
    • In dialysis, usually after 5 years
    • Tends towards articular deposition
    • High Beta-2 microglobulin is also a poor prognostic indicator in multiple myeloma

 

Presentation of amyloidosis

Dependent on site of deposition:

    • Cardiac
      • Heart failure, especially due to restrictive cardiomyopathy
      • Arrhythmias
    • Renal failure
    • Gastrointestinal
      • Vomiting, GI bleed, diarrhoea
      • Splenomegaly
    • Polyneuropathy
    • Macroglossia

 

Investigation in amyloidosis

    • Biopsy of relevant organ e.g. abdominal wall fat, salivary gland
      • Apple green birefringence under Congo red staining

 

Treatment of amyloid

  • AL amyloid
    • Treat myeloma
      • Chemotherapy (e.g. velcade and dexamethasone)
      • Autologous bone marrow transplant
  • AA amyloid
    • Treat underlying condition with the aim to reduce inflammation