Transthyretin Amyloid Cardiomyopathy Diagnosed on Incidental Myocardial Uptake During Bone Scintigraphy

An 83-year-old man underwent prostatectomy for prostate cancer. He had a history of carpal tunnel syndrome. At that time, he underwent serial ^{99 m}techinetium-hydroxymethylenediphosphonate (^{99 m}Tc-HMDP) scintigraphy for the evaluation of bone metastasis due to prostate cancer. Cardiac uptake (visual grade, 2; heart-to-contralateral [H/CL] ratio, 1.70) was incidentally observed on that first ^{99 m}Tc-HMDP scintigraphy (Figure A). Transthyretin amyloid cardiomyopathy (ATTR-CM) was suspected but he had no symptoms of heart failure, therefore further diagnostic tests were not performed.

Figure.

(A,B) ^{99 m}Techinetium-hydroxymethylenediphosphonate (^{99 m}Tc-HMDP) scintigraphy (A) 6 years earlier showing incidental cardiac uptake, and (B) recently. (C,D) Echocardiography in parasternal long-axis view (C) 6 years earlier and (D) recently, showing the change in thickness of the (1) left ventricular interventricular septum and (2) posterior wall. (E) Amyloid deposition in myocardium (Congo red). Scale bar, 50 μm.

Six years later, a second ^{99 m}Tc-HMDP scintigraphy was performed because of re-elevation of prostate-specific antigen level. The cardiac uptake was found to be stronger than noted earlier (visual grade, 3; H/CL ratio, 2.32; Figure B). Echocardiography indicated an increase in the thickness of the left ventricular interventricular septum (from 13.3 mm to 15.1 mm) and of the posterior wall (from 10.3 mm to 13.7 mm; Figure C,D), and impairment of diastolic function according to E/A ratio (from 0.56 to 0.85). Endomyocardial biopsy showed amyloid deposition in the myocardium (Figure E). Immunohistochemistry staining confirmed transthyretin presence and DNA analysis eliminated the possibility of transthyretin mutation. A final diagnosis of wild-type ATTR-CM was made.

Bone scintigraphy shows incidental cardiac uptake in 0.4% of patients aged >70 years.¹ This case illustrates the importance of cardiac uptake on bone scintigraphy, even if cardiac disease is not suspected, particularly in patients with a “red flag” for ATTR-CM, such as carpal tunnel syndrome. This knowledge needs to be shared with oncologists and radiologists.

Disclosure

None.

IRB Information

This study was approved by ethics committee of Kumamoto University (No. 2378). The study conformed to the Declaration of Helsinki and the ethics standards of ethics committees of Kumamoto University.

Reference

• 1.   Kim HM, Sohn DW, Paeng JC. Prevalence of positive ^{99 m}Tc-DPD scintigraphy as an indicator of the prevalence of wild-type transthyretin amyloidosis in the elderly. Int Heart J 2019; 60: 643–647.