Technetium-99m-labeled pyrophosphate uptake in the rectum of a patient with wild-type transthyretin cardiac amyloidosis

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.