A Case of Wild-type Cardiac Transthyretin Amyloidosis Diagnosed by Non-invasive Methods

Transthyretin amyloid cardiomyopathy was considered a rare pathology. However, recent studies show a significant prevalence in patients with degenerative aortic stenosis and heart failure with preserved ejection fraction.

An 85-year-old woman presented with a four-month history of pain in the rib cage with a history of diffuse large B-cell lymphoma of the oral cavity, essential thrombocytosis and dyslipidemia. She had no significant family history. A transthoracic echocardiogram showed degenerative aortic stenosis and normal systolic function with preserved left ventricular ejection fraction of 70%. Bone-avid tracer cardiac scintigraphy with technetium-99m-labeled hydroxymethylene diphosphonate with SPECT-CT documented grade two myocardial uptake according to the Perugini scale. MRI evidenced late patchy enhancement in the myocardium associated with diffuse subendocardial enhancement. Laboratory tests showed the absence of mutation in the transthyretin (TTR) gene, serum and urine immunofixation electrophoresis (IFE) negative for monoclonal protein and serum-free light chain (sFLC) assay with a normal kappa/lambda (K/L) ratio. All these findings were compatible with a non-invasive diagnosis of wild-type cardiac amyloidosis.

The accepted criteria for the definitive non-invasive diagnosis of amyloid cardiomyopathy are based on myocardial uptake by scintigraphy (with SPECT), serum and urine immunofixation electrophoresis, serum-free light chain assay and suggestive findings on echocardiography and/or MRI. Genetic testing should differentiate between ATTRv (v for variant) and ATTRwt (wt for wild type) forms.