**5.6 Amyloidosis**

Secondary amyloidosis is a life-threatening complication of RA. Mortality, amyloid burden, and renal prognosis significantly correlate with serum amyloid A (SAA) concentration. As amyloid deposits regressed in 60% of patients who had a median SAA concentration of less than 10 µg/ml, normalization of the SAA concentration not only prevents but also treats secondary amyloidosis (Lachmann et al., 2007). TCZ treatment almost completely normalizes the serum SAA level because IL-6 signal is essential for the expression of SAA (Hagihara et al., 2005). Therefore, TCZ is very useful for the treatment of secondary amyloidosis (Sato et al., 2009; Inoue et al., 2010).
