Progressive myocardial uptake on serial 99mTc-HMDP scintigraphy revealing preclinical transthyretin amyloid cardiomyopathy: A case report

The growing availability of disease-modifying therapies has heightened the importance of early diagnosis of transthyretin amyloid cardiomyopathy (ATTR-CM). 99m Tc-labeled bone scintigraphy is widely used for the noninvasive diagnosis of ATTR-CM; however, myocardial uptake may be overlooked when scans are performed for non-cardiac indications. We report the case of an 84-year-old woman with a history of mastectomy performed nine years earlier, who was referred to our department for evaluation of dyspnea and pleural effusions. She had undergone annual 99m Tc-hydroxymethylene diphosphonate bone scintigraphy for oncologic surveillance. A retrospective review of these serial scans revealed progressively increasing myocardial uptake over eight years prior to the clinical diagnosis of ATTR-CM. Notably, the patient remained asymptomatic despite marked myocardial uptake detected several years earlier. After recognition of this case, interdisciplinary conferences were implemented at our institution to raise awareness of incidental cardiac uptake on bone scintigraphy. This case highlights the clinical value of serial bone scintigraphy in identifying preclinical ATTR-CM and demonstrates that myocardial uptake may precede symptomatic heart failure by several years. These findings emphasize the importance of interdisciplinary collaboration to facilitate early detection and timely referral of patients with suspected ATTR-CM. Learning objective Serial bone scintigraphy may reveal progressive myocardial tracer uptake years before symptomatic transthyretin amyloid cardiomyopathy (ATTR-CM) becomes apparent. Even low-grade or incidental cardiac uptake on scans performed for non-cardiac indications may warrant careful evaluation and follow-up. Early recognition of ATTR-CM may be facilitated by integrating imaging findings with subtle clinical "red flags" and by strengthening interdisciplinary collaboration across cardiology, radiology, and oncology departments.