Classification

Different proteins can be deposited as amyloid in various tissues

• deposition can be restricted to one specific site (such as pancreas, brain, larynx) (localized amyloidosis) or can be found throughout the body (systemic amyloidosis)
  • are a many types of localized amyloidosis including cerebral endocrine, and cutaneous amyloidosis
    • only the name amyloid is identical, but the localised types of amyloid mentioned above are completely different because of different precursor proteins
      
      
• five main types of systemic amyloidosis are:
  • systemic forms of amyloid that should be distinguished from each other (four acquired and one hereditary) are AA, AL, Aß2M, and two ATTR types:
    • acquired AA amyloidosis
      • caused by chronic inflammation
      • serum amyloid A protein (SAA), an acute phase reactant, is the precursor protein of this type
      • proteinuria and loss of renal function are the most prominent clinical characteristics
        
        
    • acquired AL amyloidosis
      • caused by a plasma cell dyscrasia
      • precursor protein of this type is a kappa or lambda immunoglobulin light chain
      • clinical characteristics of this type are very diverse, such as cardiomyopathy, hepatomegaly, nephrotic syndrome, severe diarrhoea, carpal tunnel syndrome, and neuropathy (peripheral as well as autonomic neuropathy)
        
        
    • acquired Aß2M amyloidosis
      • caused by chronic dialysis because of complete renal failure
        
      • precursor protein of this type is ß2-microglobulin because high serum levels are the result of the impossibility to excrete this protein
      • clinical characteristics of this type are carpal tunnel syndrome and joint problems (shoulders, wrists, fingers, hips, vertebral column, etc.)
        
        
    • acquired ATTR amyloidosis
      • found at older age (especially older than 80 years)
      • the normal wild type precursor protein transthyretin (TTR) is the characteristic protein
      • clinically characterised by a slowly progressive cardiomyopathy
        
        
    • hereditary ATTR amyloidosis
      • caused by more than 80 autosomal dominant hereditary point mutations of the precursor protein transthyretin (TTR)
      • clinical characteristics of this type are peripheral and autonomic neuropathy, but also cardiac, renal, and ocular involvement can be seen

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Reference:

• Misumi Y, Ando Y.Classification of amyloidosis. Brain Nerve. 2014 Jul;66(7):731-7.
• Dey A. Classification of Amyloidosis.