**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Andrew Staron, Amyloidosis Center, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA, USA

**Main Body of the Abstract**
Background:  Wild-type transthyretin (ATTRwt) amyloidosis is a systemic disease. Extracardiac tissues/organs are sometimes the first site of disease identification. This study explores the spectrum of tissues/organs where ATTRwt amyloid deposits are identified and describes the outcomes of patients with non-cardiac disease.
Methods:  We studied 552 patients with ATTRwt amyloidosis seen at the Boston University Amyloidosis Center between 1994–2023 who had at least one tissue/organ biopsy stained with Congo red (CR). Median number of tissue samples per patient was 2 (total 957 biopsies). Amyloid typing and genetic analysis were performed to confirm diagnosis.
Results:  The endomyocardium and abdominal fat pad stained CR positive in 99% (203/205) and 23% (123/534) of biopsy samples, respectively. Common extracardiac sites where ATTRwt amyloidosis was detected included the tenosynovium, bone marrow, gastrointestinal tract, lungs and urinary bladder (Table 1). Of 119 patients with positive CR staining of extracardiac biopsy sites, 68 (57%) had ATTR-cardiomyopathy at the time of extracardiac biopsy; whereas 51 (43%) did not, of whom 6 (12%) subsequently developed ATTR-cardiomyopathy after a median of 2.4 years (range 0.4–22.7).
The 45 patients who did not develop ATTR-cardiomyopathy (median follow-up of 1.8 years, range 0.2–10.3) were younger (73 vs 76 years, p<.001) and more often female (18% vs 6%, p=.002) than those with ATTR-cardiomyopathy. Median overall survival was 6.8 years (95%CI, 3.3‒NR) for this non-cardiac group and 4.3 years (95%CI, 3.8‒4.6) for those with ATTR-cardiomyopathy (p=.059).
Conclusions:  ATTRwt amyloidosis is commonly identified in extracardiac tissues/organs. Some patients lack clinical features of ATTR-cardiomyopathy and have favorable outcomes.



**Author Listing - Lead/ Submitting Author (we will be communicating with this individual): Name, Institution, City and State where the work was done. Co-authors will be added in a separate section.**
Andrew Staron, Amyloidosis Center, Boston University Chobanian & Avedisian School of Medicine and Boston Medical Center, Boston, MA, USA

**Main Body of the Abstract**
**Background:**  Wild-type transthyretin (ATTRwt) amyloidosis is a systemic disease. Extracardiac tissues/organs are sometimes the first site of disease identification. This study explores the spectrum of tissues/organs where ATTRwt amyloid deposits are identified and describes the outcomes of patients with non-cardiac disease.
**Methods:**  We studied 552 patients with ATTRwt amyloidosis seen at the Boston University Amyloidosis Center between 1994–2023 who had at least one tissue/organ biopsy stained with Congo red (CR). Median number of tissue samples per patient was 2 (total 957 biopsies). Amyloid typing and genetic analysis were performed to confirm diagnosis.
**Results:**  The endomyocardium and abdominal fat pad stained CR positive in 99% (203/205) and 23% (123/534) of biopsy samples, respectively. Common extracardiac sites where ATTRwt amyloidosis was detected included the tenosynovium, bone marrow, gastrointestinal tract, lungs and urinary bladder (Table 1). Of 119 patients with positive CR staining of extracardiac biopsy sites, 68 (57%) had ATTR-cardiomyopathy at the time of extracardiac biopsy; whereas 51 (43%) did not, of whom 6 (12%) subsequently developed ATTR-cardiomyopathy after a median of 2.4 years (range 0.4–22.7).
The 45 patients who did not develop ATTR-cardiomyopathy (median follow-up of 1.8 years, range 0.2–10.3) were younger (73 vs 76 years, p<.001) and more often female (18% vs 6%, p=.002) than those with ATTR-cardiomyopathy. Median overall survival was 6.8 years (95%CI, 3.3‒NR) for this non-cardiac group and 4.3 years (95%CI, 3.8‒4.6) for those with ATTR-cardiomyopathy (p=.059).
**Conclusions:**  ATTRwt amyloidosis is commonly identified in extracardiac tissues/organs. Some patients lack clinical features of ATTR-cardiomyopathy and have favorable outcomes.



Identifying and Tracking the Evolution of Wild-Type Transthyretin (ATTRwt) Amyloidosis in Extracardiac Tissues/Organs PB70 (#211)

We invite you to attend the XIX International Symposium on Amyloidosis to be held in Rochester, MN.

This symposium is organized as a hybrid meeting (with the focus on in-person) held from Sunday, May 26 through Thursday, May 30, 2024.

Together with the ISA Board and members of Mayo Clinic, a very attractive scientific hybrid program is being planned. The program will cover a variety of types of systemic amyloidosis: ATTR (hereditary and wild-type), AL (light-chain), AA and less frequent forms. There will be key lectures, specific symposia including those company sponsored, oral presentations and poster sessions of accepted abstracts.

COURSE DESCRIPTION
This program will provide a comprehensive review of state-of-the-art education in systemic amyloidosis: basic science, pathophysiology, diagnosis, current and emerging treatments. Scientific presentations will include competitive oral and poster abstracts. The rapid evolution of scientific discovery and expanding treatment options has created tremendous interest in the field and this meeting will fill and important gap in educating scientists and clinicians.