Step‐by‐step typing for the accurate diagnosis of concurrent light chain and transthyretin cardiac amyloidosis

While (99m)Tc‐pyrophosphate scintigraphy is clearly useful in diagnosing transthyretin amyloid cardiomyopathy (ATTR‐CM), it is necessary to know the pitfalls of this test for proper use. We present a rare case of concurrent ATTR‐CM and amyloid light chain (AL) cardiomyopathy. The patient showed congestive heart failure with left ventricular hypertrophy. (99m)Tc‐pyrophosphate scintigraphy revealed abnormal cardiac uptake of Grade 3, a typical feature for ATTR‐CM. However, the patient showed renal impairment with proteinuria and the presence of monoclonal gammopathy, which rather suggested AL amyloidosis. Endomyocardial biopsy, immunohistochemistry, and proteomic analysis by laser microdissection with liquid chromatography‐coupled tandem mass spectrometry were performed, which finally confirmed both ATTR‐CM and AL cardiomyopathy. This case implicates the importance of combining examinations and precisely interpreting the results to diagnose cardiac amyloidosis accurately.