Fibrinogen A alpha chain Leu 554: an African-American kindred with late onset renal amyloidosis.

An African-American kindred with renal amyloidosis is described. Four members in two generations developed nephropathy in the sixth to eighth decade of life. Kidney biopsy and subcutaneous fat aspirate biopsy of one patient revealed amyloid deposits. DNA analysis showed that patients were heterozygous for a mutation in the fibrinogen A alpha chain gene with a guanine to thymine transversion at the second base of codon 554, predicting a leucine for arginine substitution. Peptide sequence analysis of isolated plasma fibrinogen showed normal peptide as well as variant peptide with leucine replacing arginine at position 554, as predicted by the DNA sequence. The ratio between normal and variant peptides was approximately 1:1 in one patient and 3:2 in another. Although this African-American kindred has the exact same mutation as a previously described Peruvian-Mexican kindred, the onset age in this kindred is much later than in the Peruvian-Mexican kindred. This finding may indicate the existence of additional factor(s) beside the primary causative genetic mutation, which affect the expression of the disease.