Cystatin C in serum as an early marker of renal involvement in Familial Mediterranean Fever patients.

BACKGROUND The major renal involvement in Familial Mediterranean Fever (FMF) is the occurrence of amyloidosis that primarily affects the kidneys manifested by proteinuria and ending in death from renal failure. AIM This study aims to investigate whether serum cystatin (cys-C) levels could be used as an early marker of renal involvement in FMF patients. PATIENTS AND METHODS Forty-six patients with FMF during the attack period (AP), and 41 patients with FMF during attack-free periods (AFP), and 11 patients with FMF associated amyloidosis, and 38 healthy controls were enrolled in the study. We determined cys-C levels in the serum of FMF patients and healthy controls. RESULTS Serum cys-C levels were significantly increased in patients with FMF and secondary amyloidosis, and serum cys-C is a more accurate and efficient marker for detecting renal involvement than estimated glomerular filtration rate (e-GFR) in patients with FMF. CONCLUSIONS We propose a cutoff level of the serum cys-C of 876.5 pg/mL for screening renal involvement in patients with FMF, and amyloidosis should be strongly suspected when the serum cys-C reaches 1565.5 pg/mL.