AApo A2

Rare, hereditary amyloidosis with primary renal involvement characterized by interstitial and medullary amyloid deposition in the kidney, low plasma levels of ApoA-2, and slow disease progression.

Amyloidoses are a large group of heterogeneous diseases characterized by insoluble protein and peptide aggregates aligned in a β-sheet structure forming amyloid fibrils 10 to 12 nm in diameter. More than 30 different proteins that form amyloids have now been identified. Depending on histoanatomical distribution and quantity, amyloid can cause progressive and life-threatening organ dysfunction. Variants of transthyretin, apolipoprotein AI (apoAI), apolipoprotein AII, the Aα-chain of fibrinogen, gelsolin, and lysozyme are some of the proteins known to cause hereditary amyloidosis.

Hereditary AAPoA2 amyloidosis is caused by mutations in the APOA2 gene, a protein-coding gene located on chromosome chromosome 1q23.3.

Basically, amyloid can be acquired or hereditary. Amyloid may be deposited locally or may be deposited as a systemic disease in many different organs. Because of the diversity of precursor proteins, between which there is no sequence homology, it has been impossible to find a common primary structural or functional motif that predicts the amyloidogenicity of a peptide or protein. In this regard, the hereditary amyloidoses are particularly interesting because they are caused by germline mutations that increase the propensity of the affected protein to form aggregates under certain circumstances. Important pathophysiological conclusions can be drawn from the genetic defect and the encoded "defective" protein.

The clinical manifestations of hereditary AApoA2 amyloidosis are inseparable from those of hereditary AApoA2 amyloidosis. As in the latter, they frequently affect the liver, kidney, larynx, skin, and myocardium.

Apolipoproteins are increasingly recognized in hereditary forms of amyloidosis. Although mutations in APOA1 and APOA2 are well established in hereditary amyloidosis, new mutations continue to be discovered, providing further insight into the pathogenesis of apolipoprotein-related amyloidosis. In addition, further amyloidogenic mutations have been described in APOC2 and APOC3. Although no inherited mutations in APOE or APOA4 have been described to date, both protein products are amyloidogenic and frequently found in amyloid deposits .

1. Benson MD (2003) The hereditary amyloidoses. Best Pract Res Clin Rheumatol 17: 909-927.
2. Guo Z et al (2003) Amyloidosis modifier genes in the less amyloidogenic a/j mouse strain. Lab Invest 83:1605-1613.
3. Horike K et al (2018) Two novel APOA1 gene mutations in a Japanese renal transplant recipient with recurrent apolipoprotein A-I related amyloidosis. Nephrology (Carlton) 23 Suppl 2:17-21.
4. Jeraj N et al (2021) Apolipoprotein genetic variants and hereditary amyloidosis. Curr Opin Lipidol 32(2):132-140.
5. Joy T et al (2003) APOA1 related amyloidosis: a case report and literature review. Clin Biochem 36:641-645.
6. Westermark P et al (2002) Amyloid fibril protein nomenclature-2002 Amyloid 9: 197-200.