False positive technetium-99m pyrophosphate scintigraphy in a patient with cardiac amyloidosis light chain

Abstract

Introduction: Patients with cardiac amyloidosis light chain (AL) present with negative Tc-99m pyrophosphate (PYP) scintigraphy (absent or mild heart uptake). On the contrary, patients with cardiac amyloidosis transthyretin (ATTR) present with positive Tc-99m PYP scanning (intensive heart uptake). We present a false positive Tc-99m PYP scintigraphy (grade 2, the heart-to-contralateral ratio is 1.65) in a patient with AL. Patient concerns: A 42-year-old Chinese man complained of effort intolerance, chest discomfort, and short of breath progressively over 1 year. New York Heart Association Class III. Physical examination showed legs swelling. Laboratory revealed elevated brain natriuretic peptide of 23,031 ng/mL (0–88) and Troponin-T of 273.4 ng/mL (0–14). Diagnosis: Cardiac amyloidosis light chain. Evidences: free light chains (FLCs): decreased serum free kappa/lambda ratio of 0.043 (0.31–1.56). Immunofixation electrophoresis: a positive lambda light chain monoclonal protein. Cardiac biopsy: HE: Ambiguity Congo red strain. Myocardial immunofluorescence: positive lambda light chain. Myocardial immunohistochemistry: positive lambda light chain, negative kappa light chain, and TTR. Interventions: Furosemide 40 mg qd, torasemide 20 mg qd, spirolactone 20 mg qd, potassium chloride 10 mL per 500 mL urine, atorvastatin calcium tablet 20 mg qd, aspirin enteric-coated tablets 100 mg qd during the 2-weeks in-hospital. Outcomes: The patient died 2 months later after discharge. Conclusion: False positive Tc-99m PYP scintigraphy may rarely presented in patients with cardiac amyloidosis light chain. So, the clonal plasma cell process based on the FLCs and immunofixation is a base to rule out AL cardiac amyloidosis when we interpret a positive Tc-99m PYP scintigraphy.

99mTechnetium‐pyrophosphate scintigraphy: a practical guide for early diagnosis of transthyretin amyloid cardiomyopathy

“…False‐positive cases in 99m Tc‐PYP scintigraphy for ATTR‐CM may include Grade 2 or 3 myocardial uptake; a recent history of acute myocardial infarction 54 ; AL amyloidosis 34 , 54 , 69 , 70 , 71 , 72 , 73 ; apolipoprotein AI amyloidosis (AApoAI), apolipoprotein AII amyloidosis (AApoAII), apolipoprotein A‐IV amyloidosis (ApoAAIV), or β2‐microglobulin amyloidosis (Aβ2M) 10 ; hypertrophic cardiomyopathy 74 , 75 ; hydroxychloroquine toxicity 76 ; and cardiac blood pools. 54 Case reports on false‐positive myocardial uptake following intravenous iron injections have been published for 99m Tc‐DPD and 99m Tc‐HMDP scintigraphy.…”

Fat biopsy from a pocket of cardiac implantable electronic device: An alternative diagnostic option for cardiac amyloidosis

“…Radionuclide bone scintigraphy with technetium-labeled bisphosphonates has been widely recognized as a useful test for diagnosing TTR-CA 6 ; however, false-positives in amyloid light-chain amyloidosis, hypertrophic cardiomyopathy, and false-negatives have recently been reported in multiple reports. 7 , 8 , 9 , 10 , 11 Therefore, histological confirmation of the diagnosis of amyloidosis remains essential in some cases.…”

Immunoglobulin Light Chain Amyloidosis: Diagnosis and Risk Assessment

“…Therefore, in the presence of a monoclonal protein, this nuclear imaging test cannot be used to validate typing, and tissue-based typing should be pursued. 35,36 Because the most commonly involved organs are the heart and kidneys, followed by the nerves, liver, and gastrointestinal tract, the minimal evaluation for organ involvement in patients with AL amyloidosis should include ECG, echocardiogram, cardiac biomarkers (as will be discussed later), serum creatinine, albumin, and alkaline phosphatase. 22 If suspicion exists for nerve involvement, then nerve conduction studies, electromyography, and autonomic nerve studies should be performed.…”