Hereditary systemic amyloidosis associated with a new apolipoprotein AII stop codon mutation Stop78Arg

Abstract

Background. Mutations in the gene for apolipoprotein AII (apoAII) have recently been found to cause hereditary renal amyloidosis. In each case amyloid deposition has been associated with a peptide extension at the carboxyl-terminus of apoAII, the result of mutations in the normal stop codon. Methods. A Caucasian man who has had progressive renal dysfunction since age of 34 was found to have amyloidosis on renal biopsy at age 56. Echocardiogram showed mild intraventricular septal thickness and technetium-99m (99mTc)-pyrophosphate scintigraphy demonstrated uptake by cardiac muscle consistent with amyloid deposition in the myocardium. His father died of renal failure and his paternal half brother has renal dysfunction. Results. DNA sequencing of the apoAII gene in the proband showed a T to C transition at the first position of the stop codon indicating replacement of the stop codon by L-arginine (Arg) at residue 78. Western analysis of the proband's plasma under reducing conditions using anti-apoAII revealed an extra band at approximately 10 kD in addition to the normal apoAII band at 8 kD. Western analysis of solubilized amyloid fibrils isolated from rectal biopsy tissue contained only the variant apoAII. Conclusion. These results indicate that the proband's amyloid fibrils are derived from apoAII and the amyloidogenesis is linked to the peptide extension at the carboxyl-terminus of variant apoAII. Of particular interest is that this novel apoAII variant may cause amyloid cardiomyopathy in addition to renal amyloid.