Inclusion Criteria:  Diagnosis of transthyretin amyloidosis documented by pathogenic transthyretin mutation; evidence of cardiac involvement on echocardiogram or MRI; amyloid deposit confirmed by Congo red staining or presence of myocardial scintigraphy with grade 2 or 3 uptake (with distant monoclonal gammopathy of uncertain significance (MGUS); in the presence of MGUS it is necessary to confirm the TTR protein in the tissue by immunohistochemistry or mass spectrometry. Non-consanguineous living with patients; Sign an informed consent form.  Exclusion Criteria:  Inflammatory bowel disease or persistent diarrhea for more than two weeks; Use of antibiotics and/or prebiotic or probiotic supplements in the two months prior to collection; Concurrent participation in other clinical studies.