**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.**
Emily B. Martin
University of Tennessee Graduate School of Medicine
Knoxville, TN

**Main Body of the Abstract**
Background: Lumbar spinal stenosis (LSS) is one of several recently investigated conditions thought to precede the development of systemic amyloidosis. Studies have observed amyloid in the ligamentum flavum (LF) removed during laminectomy surgery, mostly typed as transthyretin (ATTR) amyloid. However, the prevalence of amyloid-positive specimens has varied greatly from 20–80%. Here we report observations from a screening assessment at the University of Tennessee Medical Center.
Methods: Subjects ≥ 35 y without history of amyloidosis consented to LF analysis. Tissues were manually stained with alkaline Congo red (CR) solution, and amyloid load was assessed on a scale of 0–4 by an experienced reviewer. Serial tissue sections with sufficient material for immunohistochemistry (IHC) were stained with TTR and apolipoprotein-A1 (APOA1) antibodies, and a subset was stained with biotinylated amyloid-binding peptide, p5+14.
Results: The LF of 97 males (n=53) and females (mean age 64 y) was evaluated. Amyloid was detected in 88% (85/97), with half receiving a CR score=1 (Fig. A). Of the evaluable specimens, IHC was TTR-positive in 86% (36/42) and APOA1-positive in 71% (30/42); remarkably, many showed discrete regions of both types. Biotinyl-p5+14 stained LF amyloid in 100% of evaluated specimens (n= 31; Fig. B). A significant positive correlation between CR score and age was observed (rS=0.49; p<0.001).
Conclusion: Amyloid in the LF is not uncommon. Studies of the relationship between LF amyloid load and systemic amyloidosis, potentially assessed by amyloid-specific nuclear imaging with p5+14, may help define those LSS patients truly at risk of developing systemic amyloidosis.



**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.**
Emily B. Martin
University of Tennessee Graduate School of Medicine
Knoxville, TN

**Main Body of the Abstract**
**Background:** Lumbar spinal stenosis (LSS) is one of several recently investigated conditions thought to precede the development of systemic amyloidosis. Studies have observed amyloid in the ligamentum flavum (LF) removed during laminectomy surgery, mostly typed as transthyretin (ATTR) amyloid. However, the prevalence of amyloid-positive specimens has varied greatly from 20–80%. Here we report observations from a screening assessment at the University of Tennessee Medical Center.
**Methods:** Subjects ≥ 35 y without history of amyloidosis consented to LF analysis. Tissues were manually stained with alkaline Congo red (CR) solution, and amyloid load was assessed on a scale of 0–4 by an experienced reviewer. Serial tissue sections with sufficient material for immunohistochemistry (IHC) were stained with TTR and apolipoprotein-A1 (APOA1) antibodies, and a subset was stained with biotinylated amyloid-binding peptide, p5+14.
**Results**: The LF of 97 males (_n_=53) and females (mean age 64 y) was evaluated. Amyloid was detected in 88% (85/97), with half receiving a CR score=1 (Fig. A). Of the evaluable specimens, IHC was TTR-positive in 86% (36/42) and APOA1-positive in 71% (30/42); remarkably, many showed discrete regions of both types. Biotinyl-p5+14 stained LF amyloid in 100% of evaluated specimens (_n_= 31; Fig. B). A significant positive correlation between CR score and age was observed (_r_~S~=0.49; _p_<0.001).
**Conclusion:** Amyloid in the LF is not uncommon. Studies of the relationship between LF amyloid load and systemic amyloidosis, potentially assessed by amyloid-specific nuclear imaging with p5+14, may help define those LSS patients truly at risk of developing systemic amyloidosis.



Screening for amyloid in patients with lumbar spinal stenosis: A single site assessment of prevalence, type, and extent of amyloid burden in the ligamentum flavum  PB75 (#297)

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.