Exons 2, 3, and 10 of the MEFV gene, C-reactive protein (CRP), serum amyloid A protein (SAA), procalcitonin (PCT), and S100A12 concentrations, erythrocyte sedimentation rate (ESR), and differential blood count were analysed in apparently healthy parents (n=26) of homozygous children with familial Mediterranean fever (FMF).
The clinical manifestations including age at disease onset, number of FMF attacks, colchicine dose and severity score were not related to genotypes of SAA1.
Patients with FMF or a rheumatic disease and the SAA1 α/α genotype had a relative risk of 4.86 and 2.53, respectively, for developing an AA amyloidosis.
A relationship between the presence of amyloidosis and SAA1 genotype has been shown in recent studies of (principally) familial Mediterranean fever patients.
Our data indicate that SAA1 gene polymorphisms, consisting of -13T/C SNP in the 5'-flanking region and SNPs within exon 3 (2995C/T and 3010C/T polymorphisms) of SAA1 gene, are associated with susceptibility to FMF in the Japanese population.
SAA1 is one of the few modifiers identified in humans: this gene influences the risk of renal amyloidosis (RA) in patients with familial Mediterranean fever (FMF), a Mendelian autoinflammatory disorder associated with mutations in MEFV.
The genotypes of the -13T/C SNP in the 5'-flanking region of the SAA1 gene and the two SNPs within exon 3 of SAA1 (2995C/T and 3010C/T polymorphisms) were determined in 88 Greek patients with RA, 14 patients with familial Mediterranean fever (FMF) and 110 healthy controls.
Fourteen MEFV mutations were screened and the SAA1 and MICA polymorphisms tested in 30 FMF patients with amyloidosis and 40 FMF patients without amyloidosis.
In this study, we analyzed the contribution of genotypes at the MEFV and SAA1 loci to disease severity and to the development of amyloidosis, and further defined the factors affecting the clinical profile of FMF.
Overall, these data, which provide new insights into the pathophysiology of FMF, demonstrate that susceptibility to renal amyloidosis in this Mendelian disorder is influenced by at least two MEFV-independent factors of genetic origin-SAA1 and sex-that act independently of each other.
By conventional linkage analysis this eliminates a minimum of 10.4 cM including and surrounding the SAA gene cluster as the site of the FMF mutation although SAA proteins are prominent physiologic markers of the acute attacks.