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.
Prognosis:
- 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:
- Arthritis
- Carpal tunnel syndrome
- Boney cysts
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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