Key Information
Abstract
Wild-type transthyretin amyloidosis is a disease characterized by deposition of transthyretin amyloid protein in systemic organs and tissues, especially the heart, lungs, tenosynovium, and ligaments. Transthyretin amyloid is also frequently deposited in the gastrointestinal tract. Technetetium-99m-labeled pyrophosphate facilitates imaging of its depositions in the myocardium and extracardiac organs and tissues, such as subcutaneous fat and skeletal muscles. However, few reports have described the uptake of bone-seeking radiotracers in the gastrointestinal tract. This report presents the case of a 90-year-old woman diagnosed with wild-type transthyretin cardiac amyloidosis. The patient had technetetium-99m-labeled pyrophosphate uptake in the myocardium, internal oblique muscle, and rectum, which decreased or disappeared after 22 months of treatment with tafamidis. The patient had a long-standing history of constipation. However, the symptoms persisted after starting tafamidis, and their attribution to wild-type transthyretin amyloidosis was, therefore, uncertain. Technetetium-99m-labeled pyrophosphate scintigraphy can detect transthyretin amyloid deposition in the rectum of patients with wild-type transthyretin cardiac amyloidosis.
Keywords: Alimentary tract, Myocardium, Tafamidis, Technetium-99m-labeled pyrophosphate scintigraphy, Wild-type transthyretin amyloidosis
Introduction
Cardiac amyloidosis (CA) is characterized by extracellular deposition of amyloid fibril proteins in various parts of the heart, including the myocardium, vessels, valves, and pericardium [1external link, opens in a new tab]. Amyloid deposition in the myocardial interstitium is often associated with wall thickening, restricted physiology, heart failure, and arrhythmias [[2]external link, opens in a new tab, [3]external link, opens in a new tab, [4]external link, opens in a new tab]. More than 40 amyloid fibril proteins have been identified in humans, and nearly half of them are associated with systemic deposition [5external link, opens in a new tab]. From amyloid fibrils associated with systemic deposition, 10 amyloidogenic proteins have been identified to accumulate in the myocardium and cause clinically significant cardiac disease [6external link, opens in a new tab]. However, almost all clinical cases of CA involve immunoglobulin light chain (AL) or transthyretin (ATTR) amyloidosis [4external link, opens in a new tab,[6]external link, opens in a new tab, [7]external link, opens in a new tab, [8]external link, opens in a new tab]. ATTR amyloidosis is classified based on the sequence of the transthyretin gene (wild-type [ATTRwt] versus variant-type [ATTRv]).