Abstract 15218: Hereditary Transthyretin Cardiac Amyloidosis in a Patient at High Risk for Plasma Cell Dyscrasias: A Complex Diagnostic Work-Up

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Background: Cardiac amyloidosis (CA) is most commonly caused by the infiltration of misfolded amyloid transthyretin (ATTR) or light chain (AL) molecules in the myocardium. The workup for CA requires serum assessment to exclude the rapidly progressive AL subtype before imaging to assess the more common and indolent ATTR form. The diagnostic algorithm has the potential to become complex as in this case about a woman with Sjogren’s syndrome which predisposes to plasma cell dyscrasias. Case: A 68-year-old female with congenital long QT syndrome requiring implantable cardioverter-defibrillator (ICD), bilateral carpal tunnel, and recent diagnosis of Sjogren’s syndrome was found to have new systolic heart failure during workup for interstitial lung disease. Labs revealed pancytopenia, abnormal kappa/lambda ratio (2.25), and polyclonal gammopathy on immunofixation. Echocardiogram showed moderately reduced systolic function with an ejection fraction of 35-40% and moderate concentric left ventricular hypertrophy. Decision-making: Cardiology obtained cardiac magnetic resonance imaging (CMR) that returned indeterminate due to ICD artifact. Hematology performed a bone marrow biopsy that was negative for plasma cell dyscrasia, though stained positive for amyloid on congo red with mass spectrometry revealing the valine 142 isoleucine (Val142Ile) amino acid substitution consistent with hereditary ATTR-CA. To definitively assess for endomyocardial ATTR involvement the patient was sent for cardiac scintigraphy using 99mTc-labeled pyrophosphate which returned negative with a cardiac to contralateral lung uptake ratio of 1.001 and visual grade of 0. With suspicion still high, an endomyocardial biopsy was pursued and stained positive for congo red with mass spectrometry confirming hereditary Val142Ile ATTR-CA, allowing for tafamidis initiation. Conclusion: We present a complex diagnostic case of ATTR amyloid in a patient who is at high risk for plasma cell dyscrasias with an abnormal kappa/lambda ratio, non-diagnostic CMR, and negative nuclear scan. Despite significant advances in imaging techniques allowing for less invasive diagnostics, this case highlights the role of endomyocardial biopsy in complicated cases.