Amyloidosis is a group of disorders in which proteins form abnormal insoluble fibrils that infiltrate tissues, leading to organ failure.

Subtypes of amyloidosis include:
  • AL (= light chain/primary)
    • Commonest form
    • Produced by plasma cell dyscrasia
    • Associated with myeloma
    • Features include:
      • Renal involvement nephrotic syndrome
      • Cardiac infiltration – restrictive cardiomyopathy, right heart failure predominates
      • Macroglossia
      • Periorbital purpura
      • Hepatomegaly
      • Carpal tunnel syndrome
      • Sensory glove and stocking polyneuropathy
      • Autonomic dysfunction
  • AA (= serum amyloid A/secondary)
    • Associated with
      • TB
      • Rheumatoid arthritis
      • familial Mediterranean fever
      • chronic osteomyelitis
    • Commonest manifestation is renal disease
    • There may be hepatospelnomegaly
  • Familial amyloidosis
    • Autosomal dominant
    • Most commonly caused by mutations in transthyretin
    • Tend to have significant neuropathic involvement

Diagnosis is by positive congo-red staining of a tissue sample.

  • Untreated AL amyloidosis: 1 to 2 years survival (treatment is chemotherapy)
  • AA amyloidosis: depends on underlying condition
  • Familial amyloidosis: up to 15 years, depending on the underlying mutation

Dialysis-related amyloidisis
  • This is due to beta2 microglobulin not crossing the dialysis membrane
  • Features include:

Small print gem: although not considered as part of the ‘amyloidosis’ group, Down’s syndrome and Alzheimer’s disease also cause amyloid formation

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