Influence of Serum Amyloid A (SAA1) and SAA2 Gene Polymorphisms on Renal Amyloidosis, and on SAA/ C-Reactive Protein Values in Patients with Familial Mediterranean Fever in the Turkish Population AYSIN BAKKALOGLU, ALI DUZOVA, SEZA OZEN, BANU BALCI, NESRIN BESBAS, REZAN TOPALOGLU, FATIH OZALTIN, and ENGIN YILMAZ ABSTRACT. Objective. To evaluate the effect of serum amyloid A (SAA) 1 and SAA2 gene polymorphisms on SAA levels and renal amyloidosis in Turkish patients with familial Mediterranean fever (FMF). Methods. SAA1 and SAA2 gene polymorphisms and SAA levels were determined in 74 patients with FMF (39 female, 35 male; median age 11.5 yrs, range 1.0–23.0). All patients were on colchicine therapy. SAA1 and SAA2 gene polymorphisms were analyzed using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). SAA and C-reactive protein (CRP) values were measured and SAA/CRP values were calculated. Results. The median SAA level was 75 ng/ml (range 10.2–1500). SAA1 gene polymorphisms were: α/α genotype in 23 patients (31.1%), α/ß genotype in 30 patients (40.5%), α/γ genotype in one patient (1.4 %), ß/ß genotype in 14 patients (18.9%), ß/γ genotype in 5 patients (6.8 %), and γ/γ geno- type in one patient (1.4%). Of the 23 patients who had α/α genotype for the SAA1 polymorphism, 7 patients had developed renal amyloidosis (30.4%) compared to only one patient without this geno- type (1/51; 2.0%); p < 0.001. SAA2 had no effect on renal amyloidosis. SAA1 and SAA2 genotypes had no significant effect on SAA levels. SAA/CRP values were significantly lower in patients with the SAA1α/α genotype, compared to other SAA1 genotypes: 0.16 (0.025–1.96) versus 0.23 (0.012–28.20), p < 0.05. Conclusion. SAA1α/α genotype is one genetic factor that confers a significant risk for amyloidosis in the Turkish FMF population. Neither the SAA1 nor SAA2 genotypes had a significant effect on SAA level. (J Rheumatol 2004;31:1139–42) Key Indexing Terms: FAMILIAL MEDITERRANEAN FEVER AMYLOIDOSIS SERUM AMYLOID A POLYMORPHISM Familial Mediterranean fever (FMF) is a recessively inher- In 1997, 2 independent groups (French FMF Consortium ited disorder. The diagnosis is based on the occurrence of and International FMF Consortium) identified the gene recurrent episodes of fever and serous inflammation mani- responsible for FMF, designated MEFV, on chromosome 16 fested by sterile peritonitis, arthritis, and pleurisy. The (16p13.3)2,3. The most common MEFV mutations are disease primarily affects Sephardic Jews, Armenians, Turks, M694V, M680I, V726A, and M694I located on exon 10 and and North African Arabs. Amyloidosis of AA type, mainly E148Q located on exon 2. Genotype-phenotype correlation renal, is the major complication of FMF1. It develops over is not well established. There are unexplained ethnic differ- years and progresses to renal failure. ences in the rates of amyloidosis1,4-6. Although early data suggested that M694V mutation was a risk factor for From the Departments of Pediatrics, Pediatric Nephrology, and Medical amyloidosis, there are also patients with FMF who have Biology, and the Rheumatology Unit, Hacettepe University Faculty of Medicine, Ankara, Turkey. renal amyloidosis and do not carry the M694V homozygous 7-10 A. Bakkaloglu, MD, Professor of Pediatrics; A. Duzova, MD, Assistant genotype . Unidentified genetic and environmental Professor of Pediatrics; S. Ozen, MD, Professor of Pediatrics; N. Besbas, factors might have a protective or exacerbating effect on MD, Professor of Pediatrics; R. Topaloglu, MD, Professor of Pediatrics; renal amyloidosis. F. Ozaltin, MD, Fellow in Pediatric Nephrology, Department of Pediatrics, Pediatric Nephrology and the Rheumatology Unit; B. Balci, Serum amyloid A (SAA) protein family is known to PhD; E. Yilmaz, PhD, Associate Professor of Medical Biology, contain a number of differentially expressed apolipoproteins Department of Medical Biology. that are synthesized primarily by the liver. The concentra- Address reprint requests to Dr. A. Bakkaloglu, Department of Pediatrics, tion of acute phase SAA can increase to more than 1000- Hacettepe University Faculty of Medicine, 06100, Ankara, Turkey. 11 E-mail: [email protected] fold during inflammation . Its sensitivity was shown to be Submitted August 26, 2002; revision accepted January 6, 2004. equal or more than that of C-reactive protein (CRP) in Personal non-commercialPersonal, non-commercial use only. use The only. Journal The Journal of of RheumatologyRheumatology. Copyright Copyright© 2004. All rights © reserved. 2004. All rights reserved Bakkaloglu, et al: SAA gene polymorphisms 1139 Downloaded on September 23, 2021 from www.jrheum.org several studies; persistently high SAA levels were correlated SAA measurement. SAA levels were measured by solid phase sandwich with activity of rheumatic disease, rapid progression of ELISA method (Cytoscreen, Human SAA immunoassay kit; Biosource secondary amyloidosis, and poor outcome in patients under- International, Camarillo, CA, USA). The normal SAA level was < 10 ng/ml. Blood samples for SAA and CRP measurements were drawn at least 12,13 going certain surgical interventions . 2 weeks after an FMF attack. This period was chosen since we aimed to Acute phase isotypes of human SAA are encoded at 2 measure subclinical inflammation in these patients and not levels during an different loci, SAA1 and SAA2. SAA3 is a pseudogene14. It attack. The SAA/CRP ratio was calculated. has been suggested that AA-fibrils deposited in tissues were Analysis of polymorphisms in SAA1 and SAA2 genes. The SAA1 α, ß, and predominantly derived from SAA1α15. SAA1 and SAA2 are γ isoforms are encoded by the V52-A57, A52-V57, and A52-A57 SAA1 α serum precursors of amyloid A1 (AA1) and A2 (AA2) alleles, respectively. The SAA2 and ß isoforms are encoded by the H71 and R71 SAA2 alleles. These polymorphisms are located in the coding proteins, the principal components of the secondary amyloid region of the gene. SAA1 and SAA2 gene polymorphisms were analyzed plaques. Although prolonged high plasma levels of SAA using polymerase chain reaction-restriction fragment length polymorphism may lead to the deposition of its products, AA proteins, in (PCR-RFLP), as described23. SAA2 gene polymorphism was available in tissues, high concentrations of SAA are not sufficient to 69 patients. promote the development of amyloidosis. Recent studies Statistical analysis. Results were expressed as median (minimum- have focused on the polymorphisms of SAA as the genetic maximum) for data not showing normal distribution and as mean ± stan- 16-18 dard deviation (SD) for data showing normal distribution. Mann-Whitney background for amyloidogenesis . U and chi-squared tests were used for comparison. P values < 0.05 were Recently, Cazeneuve, et al showed in a group of considered significant. Armenian patients with FMF that the SAA1α/α genotype was associated with a 7-fold increased risk for renal amyloi- RESULTS dosis, compared with other SAA1 genotypes19. No correla- Clinical features, MEFV mutation analysis, and distribution tion with SAA levels was examined. of SAA1 and SAA2 gene polymorphisms are summarized in There is continuous subclinical inflammation in patients Table 1. Median age at onset of clinical symptoms was 3 with FMF20. Our group has previously shown that FMF (0.5–13) years, median age at diagnosis was 7 (1–16) years. patients homozygous and compound heterozygous for The mean duration of FMF was 7.5 ± 4.40 years (range MEFV mutation had higher SAA levels compared to 1–15) and duration of colchicine prophylaxis 3.50 ± 3.64 heterozygotes21. Elevated SAA levels in FMF patients can years (range 1–13). Colchicine dosage ranged from 0.5 to be secondary to either subclinical inflammation or to SAA1 genotype. It is well known that CRP correlates markedly with SAA in most inflammatory disorders, and that no study Table 1. Clinical characteristics, MEFV mutation analysis, and SAA1 and has reported the effect of a genetic factor in producing a SAA2 gene polymorphisms of 74 patients with FMF. variation in serum CRP levels. The SAA/CRP ratio can be a Features n (%) useful measure when evaluating the relation between SAA values and SAA1 genotypes in patients with continuous M/F 35/39 inflammation22. Current age, yrs median, (minimum-maximum) 11.5 (1–23) We evaluated the influence of SAA1 and SAA2 poly- Amyloidosis 8/74 (10.8) Consanguinity 20/74 (27.0) morphisms on renal amyloidosis, SAA level, and SAA/CRP Family history 34/74 (45.9) values in Turkish patients with FMF. History of appendectomy 7/74 (9.5) Clinical features MATERIALS AND METHODS Fever 70/74 (94.6) Patients. SAA1 and SAA2 gene polymorphisms and SAA levels were Abdominal pain 69/74 (93.2) determined in 74 FMF patients (39 female, 35 male; median age 11.5 yrs, Pleurisy 34/74 (45.9) range 1.0–23.0) who were homozygous or compound heterozygous for Arthritis/arthralgia 59/74 (69.7) MEFV mutation (M694V, M694I, M680I, V726A, and E148Q). MEFV mutations Homozygous or compound heterozygous patients were recruited in order to M694V/M694V 44/74 (59.5) clarify the effect of MEFV genotype on SAA level21. M694V/M680I 21/74 (28.4) The clinical data were registered on a standardized form that included M694V/V726A 9/74 (12.2) age, sex, familial consanguinity, history of the disease, age at onset of SAA1 genotypes α α symptom(s), presence of fever, abdominal pain, pleurisy, joint pain, duration / 23/74 (31.1) α of FMF disease, duration of colchicine prophylaxis, and colchicine dosage. /ß 30/74 (40.5) α γ All patients were on colchicine therapy and drug compliance was estimated / 1/74 (1.4) to be good. Informed consent was obtained from the patient or the parents. ß/ß 14/74 (18.9) ß/γ 5/74 (6.8) Mutation analysis.