Abstract
Objective To clarify the underlying diseases, clinical manifestations, and treatment strategies for Amyloid A (AA) amyloidosis (AAA) in Japanese patients. Methods We conducted a survey on Japanese patients with AAA treated between January 1, 2012, and December 31, 2014. Results A total of 199 patients with AAA were included in the present study. The underlying diseases of AAA were rheumatoid arthritis (60.3%), uncharacterized inflammatory disorders (11.1%), neoplasms (7.0%), other rheumatic diseases (6.5%), inflammatory bowel diseases (4.5%), chronic infection (4.5%), Castleman's disease (4.0%), and autoinflammatory diseases (2.0%). The clinical manifestations at the diagnosis of AAA were moderate to severe renal dysfunction (46.2%), moderate to severe proteinuria (30.7%), intractable diarrhea (32.2%), melena (4.5%), paralytic ileus (3.5%), heart failure (11.6%), cardiac conduction disturbances (10.1%), arrhythmia (5.5%), and hypothyroidism (11.6%). Diagnostic biopsies were performed most frequently in the gastrointestinal tract (66.3%), followed by the kidneys (22.1%), heart (5.5%), abdominal fat (4.0%), and others (3.0%). Biologics were used to treat 97 patients with AAA (48.7%). Tocilizumab (TCZ) was administered to 66 patients, with 95.5% showing good responses. Anti-TNF agents were administered to 27 patients, with 74.1% showing good responses. The treatment effects of TCZ were significantly superior to those of anti-TNF agents (p<0.007). Conclusion The most common underlying diseases of AAA were rheumatic diseases. Uncharacterized inflammatory disorders and neoplasms were also frequently observed in patients with AAA. Renal and gastrointestinal manifestations were common and important for the diagnosis of AAA, with cardiac manifestations also being of significance. Biologics, particularly TCZ, were effective therapeutic modalities.