Yield of noncardiac biopsy for the diagnosis of transthyretin cardiac amyloidosis.

Transthyretin (ATTR) cardiac amyloidosis may be because of mutant transthyretin causing familial amyloid cardiomyopathy (FAC) or wild-type transthyretin causing systemic senile amyloidosis (SSA). Histologic confirmation is often challenging and may require endomyocardial biopsy (EMB). The purpose of this study was to determine the frequency of amyloid protein deposition in positive noncardiac organ biopsy or fat aspiration in patients with ATTR cardiac amyloidosis. The medical records of 286 patients (mean age 66 ± 11, 85% men) with a diagnosis of ATTR cardiac amyloidosis at our institution who underwent noncardiac biopsy or subcutaneous fat aspiration were reviewed, including 186 patients (65%) with FAC and 100 patients (35%) with SSA. One hundred and thirty-one patients (46%) had EMB, all of which were positive. There were 210 patients (73%) with positive noncardiac tissue sampling, including 175 patients (94%) with FAC and 35 patients (35%) with SSA (p <0.001). There were 141 patients (76%) with FAC and 84 patients (84%) with SSA who underwent fat aspiration, and 67% and 14% were positive, respectively, whereas 100 (54%) and 64 (64%) underwent bone marrow biopsy, and 41% and 30% were positive, respectively. Rectal and sural nerve biopsies were performed in 52 (28%) and 54 (29%) patients with FAC and were positive in 81% and 83%, respectively. Biopsy of other noncardiac sites was performed with relatively lower frequency. In conclusion, although EMB is more commonly required to establish the diagnosis of SSA than FAC, noncardiac biopsy or fat aspiration could be considered as initial testing in patients evaluated for ATTR cardiac amyloidosis with characteristic echocardiography findings.