Cardiac Light Chain Deposition Disease Mimicking Immunoglobulin Light Chain Amyloidosis: Two Branches of the Same Tree.

September 2020 1 Arata Osanami, MD Toshiyuki Yano, MD, PhD Genzou Takemura, MD, PhD Hiroshi Ikeda, MD Masafumi Inyaku, MD Yuki Toda, MD Naoyuki Kamiyama, MD Hirohito Sugawara, MD Yufu Gocho, MD Takefumi Fujito, MD Nobutaka Nagano, MD Satoko Takahashi, MD Atsuko Muranaka, MD, PhD Marenao Tanaka, MD, PhD Norihito Moniwa, MD, PhD Kazuyuki Murase, MD, PhD Kohichi Takada, MD, PhD Hiroyuki Kuroda, MD, PhD Yayoi Ogawa, MD, PhD Tetsuji Miura, MD, PhD A 49-year-old woman with congestive heart failure was referred to our hospital. Her past medical history and family history were unremarkable. Laboratory data revealed an elevated NT-proBNP (N-terminal pro-B-type natriuretic peptide) level of 49 968 pg/mL together with increased levels of troponin T (0.059 ng/mL). Transthoracic echocardiography showed left ventricular hypertrophy (Figure [A]; maximal left ventricular wall thickness, 13.9 mm; left ventricular mass index, 124 g/m2); and left ventricular diastolic dysfunction (peak myocardial velocity during early diastole, 5.1 cm/s in the septum). Mean global longitudinal strain of the left ventricle was apparently low (−9.4%), and a polar map of global longitudinal strain showed apical sparing (Figure [B]). In addition, the elevation of the left ventricular T1 value was observed in noncontrast cardiac magnetic resonance imaging (T1 value, 1108 ms; Figure [C]), a typical finding of cardiac amyloidosis. However, electrocardiography did not indicate either low voltage or high voltage of the QRS complexes. Both kidneys were found to be enlarged in a computed tomography scan (Figure [D]), and elevated serum creatinine level (2.4 mg/dL) and proteinuria were observed. Her symptom was relieved after initiation of diuretic therapy, but her renal function progressively worsened over a period of 2 weeks. Results of free light chain (FLC) analysis showed a marked elevation in serum FLC-κ level (11 200 mg/L, normal range: 3.3–19.4 mg/L) with an abnormal κ/λ ratio of 1167 (normal range: 0.26–1.65). Results of serum and urine immunofixation were also positive for κ light chains. These findings prompted us to perform endomyocardial and renal biopsies on suspicion of immunoglobulin light chain (AL) amyloidosis. In light microscopic analyses of endomyocardial and renal biopsy specimens, Congo red staining was negative for amyloid (Figure [E]). However, deposition of FLC-κ, but not FLC-λ, in the myocardial interstitium was found in immunofluorescence analyses (Figure [F]). Results of electron microscopic analyses showed no evidence of amyloid fibril deposition. However, numerous granular and nonfibrillar electron-dense deposits were found around small vessels and cardiomyocytes in the entire areas of the endomyocardial biopsy specimens (Figure [G]). Similar deposits were also observed along and inside the endocardial layer of the myocardium (data not shown). In renal biopsy specimens, similar electron-dense deposits were found in the glomeruli and tubules. Taken together with results showing increased plasma cells in bone marrow biopsy (>10%), a diagnosis of light chain deposition disease (LCDD) associated with multiple myeloma was made. Treatment with bortezomib, a proteasome inhibitor, in combination with dexamethasone was initiated. Serum FLC-κ level was successfully reduced to 129 mg/L over a period of 3 months, but her renal function progressively deteriorated and maintenance hemodialysis was commenced. However, her cardiac function was stable, although catheter ablation was required to terminate her atrial flutter. She was transferred to an affiliated hospital for continuation of treatment and rehabilitation. © 2020 American Heart Association, Inc. CARDIOVASCULAR IMAGES