Abstract
Background
Suspicion and diagnosis of transthyretin cardiac amyloidosis (ATTR-CM) in patients with clinically significant plasma cell disorders is challenging. Timely identification of both light chain (AL) and ATTR-CM is essential for optimizing patient outcomes.
Case Summary
We report 6 patients with clinically significant plasma cell disorders diagnosed with concomitant ATTR (4 variant and 2 wild-type), in whom genetic testing and endomyocardial biopsy led to accurate diagnosis.
Discussion
This case series highlights the diagnostic pitfall of assuming patients with suspected cardiac amyloidosis and clinically significant plasma cell dyscrasias have AL-CM. Tissue confirmation is required to accurately subtype cardiac amyloidosis in patients with plasma cell dyscrasias. Genetic testing is a valuable adjunct to refine pretest probability of ATTR-CM, particularly when diagnosis is uncertain or biopsy is deferred.
Key words: awareness, diastolic heart failure, restrictive
Visual Summary
Visual Summary.
Diversity in Presentation of Cardiac Amyloidosis
Cardiac amyloidosis can present across a diverse clinical spectrum, including ATTR-CM, ATTR-CM with concomitant plasma cell dyscrasias, AL-CM, and dual AL and ATTR pathology. AL = light chain; AL-CM = light chain amyloidosis; ATTR-CM = transthyretin amyloidosis; MGUS = monoclonal gammopathy of undetermined significance; MM = multiple myeloma; sMM = smoldering multiple myeloma; TTR = transthyretin.
The majority of amyloid cardiomyopathy results from myocardial deposition of misfolded protein of monoclonal immunoglobulin light chains (AL-CM) or transthyretin (ATTR-CM).1 The diagnostic landscape has evolved, with the majority of ATTR-CM diagnosed noninvasively, whereas AL-CM typically requires tissue biopsy.1 Given the distinct treatments for ATTR and AL-CM, accurate diagnosis is vital.1 We present a case series illustrating the diagnostic complexity of cardiac amyloidosis in patients with plasma cell disorders and highlight the role of endomyocardial biopsy (EMB) and genetic testing for accurate diagnosis. All EMB samples were confirmed with mass spectrometry in our cohort (Mayo Laboratories; Rochester, Minnesota).
Take-Home Messages
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ATTR-CM can occur in patients with clinically significant plasma cell dyscrasias, including smoldering myeloma and multiple myeloma, or can rarely coexist with AL-CM.
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In patients with a monoclonal gammopathy, noninvasive testing cannot be used to diagnose AL or ATTR-CM, and endomyocardial biopsy is needed to definitively classify the subtype.
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Genetic testing is an important adjunct in the diagnostic pathway for evaluation of ATTR-CM in patients with plasma cell dyscrasias.
ATTR-CM in Clinically Significant Plasma Cell Dyscrasias
Patient 1
A 64-year-old Black man presented with progressive dyspnea and was diagnosed with heart failure with reduced ejection fraction. Transthoracic echocardiography (TTE) showed concentric hypertrophy with a left ventricular ejection fraction (LVEF) of 40% to 45%. He was treated with guideline-directed medical therapy, although this was later discontinued given hypotension. Cardiac magnetic resonance imaging (CMR) demonstrated LVEF of 36%, concentric hypertrophy with abnormal T1 nulling, and diffuse left ventricular late gadolinium enhancement (LGE) (Table 1) concerning for cardiac amyloidosis (CA). Serum studies revealed an IgA kappa monoclonal gammopathy, with a κ/λ ratio of 77. Positron emission tomography/computed tomography revealed multiple lytic lesions, and bone marrow biopsy (BMB) showed 70% plasma cells with no amyloid, consistent with multiple myeloma (MM). His heart failure (HF) was presumed secondary to AL-CM. He was treated with bortezomib, as well as daratumumab, lenalidomide, and dexamethasone (Dara-RVd), with subsequent normalization of light chains.
Table 1.
Summary of Demographics, Clinical Data, and Follow-Up in Patients With ATTR-CM and Clinically Significant Plasma Cell Disorders
| hATTR-CM and MM Patient 1 | hATTR-CM and sMM |
wt-ATTR and MM Patient | High-Risk MGUS and wtATTR Patient 5 | Coexisting AL and ATTR-CM Patient 6 | ||
|---|---|---|---|---|---|---|
| Patient 2 | Patient 3 | |||||
| Age, y/Sex | 64/Male | 67/Male | 67/Female | 84/Female | 76/Male | 78/Male |
| Race | Black | Black | White | Black | White | Black |
| TTR genotype | V122I | V122I | V30M | Negative | Negative | V122I |
| NT-proBNP, pg/mL | 4,981 | 1,758 | 266 | 759 | 1,143 | 22,687 |
| eGFR, mL/min/1.73 m2 | 49 | 61 | 91 | 51 | 39 | 20 |
| κ/λ ratioa | 77.0 | 40.03 | 0.05 | 109.26 | 28.64 | 0.05 |
| SIFEa | IgA kappa | Negative | Negative | Negative | IgA kappa | IgG lambda |
| M spike (g/dL)a | ND | ND | ND | 0.11 | 0.36 | 5.3 |
| Bone marrow biopsy | 50%-60% plasma cells | 10%-15% plasma cells | 35% plasma cells | 20%-25% plasma cells, Congo red positive with AL amyloid | 5% plasma cells; high risk cytogenetics profile (t[14; 16] and 1q amplification). | 10%-20% plasma cells |
| EMB with mass spectrometry | hATTR-CM | No amyloid | hATTR-CM | Not completed; patient deferred | wtATTR | AL (lambda) and ATTR-CM |
| Echocardiogram (nearest to time of ATTR-CM diagnosis) | LVEF 20%-25%; moderate cLVH; GLS –9.2% with apical sparing; IVSd 1.6 cm | LVEF 30%-35%; mild cLVH; IVSd 1.2 cm | LVEF 66%; normal LV wall thickness; IVSd 1.06 cm; GLS –19.9% | LVEF 65%-70%; severe cLVH; IVSd 1.6 cm; GLS –11.6%; biatrial enlargement | LVEF 25%-30%; mild cLVH; IVSd 0.83 cm; GLS –9.3%; mild biatrial enlargement | LVEF 55%-60%; moderate cLVH; IVSd 1.5 cm; GLS unmeasured but seen with apical sparing |
| CMR | Abnormal nulling pattern on T1 scout; diffuse heterogenous LGE of the LV myocardium sparing the immediate subendocardial surface | cLVH with apical sparing; multifocal subendocardial LGE in the basal and midcavity of the LV, near transmural in inferior wall; biatrial dilatation; normal nulling pattern | None | cLVH, RV hypertrophy, left atrial enhancement; normal nulling pattern | Not performed | Extensive subendocardial and transmural LGE with abnormally shorter null time; biatrial dilatation |
| Tc-99m PYP scan | Not performed | Grade 3 uptake | Grade 3 uptake | Grade 0 uptake | Not performed | Grade 1 uptake |
| Treatment | Daratumumab, lenalidomide, bortezomib, and dexamethasone; TTR stabilizer | Daratumumab; TTR stabilizer | Daratumumab, lenalidomide, dexamethasone; daratumumab; cyclophosphamide TTR silencer | Daratumumab | TTR stabilizer | Cyclophosphamide, bortezomib, and daratumumab |
| Outcome | Underwent heart transplantation | Stable cardiac disease | Stable cardiac disease | Stable cardiac disease | Stable cardiac disease | Died 3 wk after diagnosis |
AL = amyloid light-chain; cLVH = concentric left ventricular hypertrophy; CMR = cardiac magnetic resonance; eGFR = estimated glomerular filtration rate; EMB = endomyocardial biopsy; GLS = global longitudinal strain; h/wATTR = hereditary/wild type transthyretin amyloidosis; Ig = immunoglobulin; IVSd = interventricular septal thickness in diastole; κ/λ ratio = kappa-to-lambda free light chain ratio; LGE = late gadolinium enhancement; LV = left ventricle; LVEF = left ventricular ejection fraction; MGUS = monoclonal gammopathy of undetermined significance; MM = multiple myeloma; M-spike = monoclonal protein spike; ND = not detected; NT-proBNP = N-terminal pro–B-type natriuretic peptide; RV = right ventricle; SIFE = serum immunofixation electrophoresis; sMM = smoldering multiple myeloma; Tc-99m PYP = technetium-99m pyrophosphate; TTR = transthyretin.
Values checked at time of presentation.
Given worsening HF despite hematologic response, and nearly 1.5 years after initial diagnosis, he was referred to our center. TTE showed LVEF of 20% to 25% with increased wall thickness and abnormal global longitudinal strain. Transthyretin (TTR) genetic testing identified the V122I (p. V142I) variant, and subsequent EMB confirmed hereditary ATTR-CM (hATTR-CM) without evidence of AL-CM. Given advanced HF at time of this diagnosis, he underwent heart transplantation.
Patient 2
A 67-year-old Black man presented with dyspnea. He was diagnosed with atrial fibrillation with LVEF 40% attributed to tachycardia-mediated cardiomyopathy. Seven years after initial presentation, he developed a subdural hematoma, and during evaluation for coagulopathy, was found to have a kappa light chain gammopathy (κ/λ ratio: 40.03). BMB demonstrated 10% to 15% kappa-restricted plasma cells consistent with smoldering multiple myeloma (sMM). He then developed ventricular tachycardia requiring cardioversion. Coronary angiogram did not show obstructive disease. Subsequent CMR 10 years after initial presentation demonstrated concentric hypertrophy with relative apical sparing, multifocal subendocardial and transmural LGE in the basal and midcavity of the left ventricle, and biatrial dilation concerning for CA (Figure 1). Given his sMM, EMB was performed to evaluate for AL-CM, though this was negative. Genetic testing, pursued because of HF with arrhythmia, was positive for V122I. Technetium-99m pyrophosphate (PYP) scintigraphy demonstrated grade 3 uptake.
Figure 1.
Cardiac Imaging and Biopsy Pathology From a Patient With Smoldering Multiple Myeloma and Hereditary (V122I) ATTR-CM
Images from patient 2 in our case series, including (A) LGE on CMR in a nonischemic pattern at the base with multifocal subendocardial (white arrow), transmural inferolateral (open arrow), and right-ventricular side of the septum (white arrowhead). (B) CMR 4-chamber cine at end-diastole showing basal septal hypertrophy of 20 mm (double-headed white arrow, confirmed on short axis) with relative apical sparing. (C) SPECT-CT fusion short-axis image with PYP uptake in the inferoseptum (white arrowhead) and inferolateral wall (open arrow) in the same segments as LGE. (D) Second endomyocardial biopsy with Masson trichrome staining demonstrating a small amount of perimyocytic collagen (blue). No definite amyloid is identified. (E) Second endomyocardial biopsy with H&E staining demonstrating mild interstitial fibrosis and mild myocyte hypertrophy. CMR = cardiac magnetic resonance; H&E = hematoxylin and eosin; LGE = late gadolinium enhancement; PYP = technetium-99m pyrophosphate; SPECT-CT = single-photon emission computed tomography–computed tomography.
Repeat EMB 6 months later was negative for amyloid but did reveal a small amount of perimyocytic collagen on histopathology, possibly representing an amyloid precursor. He was recommended to start a TTR stabilizer as well as daratumumab plasma cell–directed therapy for his sMM.
Patient 3
A 67-year-old White woman presented with neuropathy and was found to have a lambda light chain gammopathy (κ/λ ratio: 0.05) with no M-spike detected. Initial BMB showed 5% to 10% plasma cells, although repeat biopsy 4 years later demonstrated 35% plasma cells with negative Congo red staining. After negative positron emission tomography/computed tomography, she was diagnosed with sMM. In the context of progressive peripheral neuropathy, she received daratumumab-based therapy, including daratumumab, lenalidomide, and dexamethasone (Dara-Rd). Despite this, her neuropathy progressed, for which she underwent nerve biopsy that confirmed TTR deposition. Genotype testing identified V30M (p. V50M) mutation, after which she started on patisiran.
She later underwent EMB given development of mild HF symptoms, consistent with V30M hATTR-CM. She was transitioned to vutrisiran, and her sMM has remained stable.
Patient 4
An 84-year-old Black woman with a history of atrial flutter, chronic kidney disease (CKD), and monoclonal gammopathy of undetermined significance (MGUS) presented with progressive fatigue and dyspnea. TTE findings of left ventricular hypertrophy with biatrial enlargement and aortic stenosis, with known MGUS, raised concern for AL-CM (Figure 2). Monoclonal protein studies showed kappa light chain gammopathy (κ/λ ratio: 109.26) with an M-spike of 0.11 g/dL. BMB showed 20% to 25% clonal plasma cells, and Congo red positivity with mass spectrometry subtyping confirmed AL (kappa) amyloid, after which she was started on plasma cell therapy. As part of neuropathy evaluation, she underwent skin biopsy, which was Congo red–positive with positive TTR immunofluorescence (Figure 2D). TTR genotype testing was negative. EMB was recommended, but the patient deferred. PYP scintigraphy was performed instead and demonstrated grade 0 uptake. The patient's presentation was felt to be most consistent with AL-CM, without evidence of ATTR polyneuropathy on objective testing, thus no TTR treatment was started.
Figure 2.
Cardiac Imaging and Skin Biopsy Pathology From a Patient Diagnosed With Multiple Myeloma and TTR on Skin Biopsy
Images from patient 4 in our case series, including (A) CMR 4-chamber image showing left atrial wall enhancement (white arrow), typical of amyloidosis. (B) Short-axis blood null PSIR LGE image showing nonspecific nonischemic pattern of the subepicardial and midwall LGE in the basal inferoseptal wall extending into the right ventricle (white arrow). LGE in the anterior right ventricle insertion point (white arrowhead). (C) Skin biopsy demonstrating Congo red–positive amyloid deposition within the dermis under light microscopy (×400). (D) Immunohistochemistry with anti-TTR showing expression in dermis (×200). CMR = cardiac magnetic resonance; LGE = late gadolinium enhancement; PSIR = phase sensitive inversion recovery; TTR = transthyretin.
Patient 5
A 76-year-old White man with a history of sick sinus syndrome with subsequent pacemaker, atrial fibrillation, bicuspid aortic valve, heart failure with reduced ejection fraction (LVEF of 35%-40%), and bilateral carpal tunnel syndrome presented with functional decline. TTE showed decline in LVEF to 25%, dilated left atrium, and moderate aortic stenosis. Coronary angiography demonstrated mild atherosclerosis. Monoclonal studies showed an IgA kappa gammopathy (κ/λ ratio 28.64) with M-spike of 0.36 g/dL raising concern for AL-CM. Initial EMB demonstrated amyloid deposition but was insufficient for mass spectrometry. BMB showed 5% plasma cells without amyloid deposition, consistent with MGUS. His MGUS demonstrated high-risk features, including a markedly abnormal κ/λ ratio and high-risk cytogenetics abnormalities (t[14; 16] and 1q amplification).
EMB was subsequently repeated, with mass spectrometry now identifying ATTR. TTR genotype testing was negative, consistent with wild-type ATTR. The patient was started on tafamidis, and following optimization rhythm and valve replacement, his LVEF improved to 55% to 60%. Monoclonal studies have remained stable without therapy.
Dual AL and ATTR-CM
Patient 6
A 78-year-old Black man with hypertension, obesity, diabetes, CKD, atrial fibrillation, and HF with preserved ejection fraction presented with acute decompensation. TTE showed LVEF of 55% to 60% with increased wall thickness. Monoclonal studies revealed IgG lambda monoclonal gammopathy (κ/λ ratio: 0.05) with an M-spike of 5.3 g/dL. CMR showed extensive subendocardial and transmural LGE. BMB demonstrated 10% to 20% lambda-restricted plasma cells without Congo red positivity. EMB confirmed presence of both AL and ATTR amyloid deposition, with negative TTR genotype testing. He started on cyclophosphamide, bortezomib, and daratumumab but developed progressive cardiogenic shock and renal failure. Given poor prognosis, he transitioned to comfort-focused care and died shortly thereafter.
Discussion
We present the diagnostic complexity of ATTR-CM in patients with clinically significant plasma cell disorders (Table 1). Across 6 patients, we describe 5 clinically important scenarios: MM coexisting with hereditary ATTR-CM (patient 1), sMM coexisting with hereditary ATTR-CM (patients 2 and 3), MM and AL-CM (patient 4), high-risk MGUS coexisting with wild-type ATTR (patient 5), and dual AL and ATTR-CM (patient 6).
According to the 2023 American College of Cardiology expert consensus decision pathway on cardiac amyloidosis, contemporary diagnosis of CA begins with monoclonal protein testing, and if abnormal, biopsy of the affected organ or a surrogate site is recommended. In patients with suspected cardiac involvement, EMB with mass spectrometry is preferred given the variable sensitivity for surrogate sites.2 EMB for AL-CM is particularly time sensitive when no other tissue diagnosis or hematologic indication for therapy is present. In practice, EMB may be deferred when noncardiac tissue is confirmatory of AL or when treatment is already indicated for an underlying plasma cell disorder such as MM. Our cases highlight a diagnostic pitfall of presuming that suspected CA in patients with clinically significant plasma cell disorders (ie, MM, sMM, or high-risk MGUS) is AL-CM. ATTR-CM can coexist across all types of plasma cell dyscrasias (Table 2).3, 4, 5 Additionally, AL amyloid is a well-established cause of false-positive scintigraphy scans.6 Thus, a positive scan cannot exclude AL-CM when a plasma cell dyscrasia is present, and tissue biopsy with mass spectrometry remains essential.
Table 2.
Description of Diagnostic Criteria and Monoclonal Protein Profiles for the Spectrum of Plasma Cell Dyscrasias
| Plasma Cell Dyscrasia | Diagnostic Criteria | Most Common Monoclonal Protein Profiles |
|---|---|---|
| MGUS (non-IgM, IgM, light-chain) |
|
|
| sMM |
|
|
| MM |
|
|
| AL amyloidosis |
|
|
AL = amyloid light-chain; BMB = bone marrow biopsy; BMPC = bone marrow plasma cell; CRAB = hypercalcemia, renal insufficiency, anemia, bone lesions; FLC = free light chain; IFE = immunofixation electrophoresis; Ig = immunoglobulin; MGUS = monoclonal gammopathy of undetermined significance; MM = multiple myeloma; MRI = magnetic resonance imaging; sMM = smoldering multiple myeloma; SLiM = ≥60% clonal bone marrow plasma cells, serum free light chain ratio ≥100, or >1 focal lesion on magnetic resonance imaging.
MGUS frequently coexists with ATTR-CM, reflecting the shared age-dependent prevalence.2 Interpretation is further complicated by CKD, which is common with ATTR-CM, and impairs clearance of kappa free light chains.2,3 While kappa-predominant abnormalities may be seen in patients with renal insufficiency, lambda-predominant abnormalities are not explained by renal dysfunction and strongly suggest an underlying monoclonal process.3,4 Notably, AL amyloidosis demonstrates a marked lambda predominance. When present, this confers a higher pretest probability of AL-CM and warrants expedited EMB.3,4 Although the presence of any monoclonal protein warrants strong consideration for tissue confirmation, factors including predominant light chain subtype and renal function may influence the threshold for pursuing EMB in clinical practice.2,3 While age- and eGFR-adjusted light chain ratio reference ranges have been developed to help guide EMB decisions, further validation across diverse cohorts and clarification of long-term prognostic implications are needed.
Although rare, coexisting AL and ATTR-CM is an important diagnostic consideration that we have previously described in 3 patients from our cohort and now with patient 6.7 Suspicion for coexisting AL and ATTR-CM should arise when features suggestive of AL-CM are present simultaneously with ATTR characteristics (older age, male sex, family history of HF or amyloidosis, and musculoskeletal symptoms such as spinal stenosis and spontaneous biceps tendon rupture).2 Recognition of coexisting AL and ATTR is critical for appropriate prognostic discussions and treatment. Importantly, treatment of MGUS or sMM is not routinely recommended, although the latter is being evaluated in clinical trials. In patient 3, plasma cell–directed therapy was pursued because of progressive neuropathy raising concern for occult light chain–mediated disease despite negative biopsy results, reflecting individualized management rather than standard therapy.
TTR genotype testing can serve as an important adjunct test in patients with plasma cell dyscrasias and suspected CA. The V122I variant is present in 3.5% of Black individuals in the United States and is associated with increased risk of cardiomyopathy.2 If EMB cannot be expeditiously pursued, genetic testing can be pursued in patients with high-risk features such as Black race, family history of HF or amyloidosis, or presence of polyneuropathy. In patient 1, genetic testing was pursued given worsening HF despite hematologic improvement, which led to identification of the pathogenic V122I variant. Notably, interpretation of his worsening HF was complicated by exposure to lenalidomide-based therapy, as immunomodulatory agents have been associated with cardiovascular toxicity in patients with CA.1,7 Thus, it is difficult to determine the extent to which this patient's progressive HF reflected treatment-related cardiotoxicity vs progression of underlying hATTR-CM.8
While EMB remains the gold standard for CA diagnosis, we highlight a limitation (patient 2 and patient 5), particularly as patients with ATTR-CM are being diagnosed at earlier disease stages.2 The diagnostic accuracy of EMB is vulnerable to sampling error because of heterogenous myocardial distribution of amyloid and depends on the location as well as number of biopsy specimens.8 In the case of patient 2, despite 2 negative EMBs, the combination of grade 3 PYP uptake, characteristic imaging findings, identification of the V122I variant, and fibrillar material on EMB possibly representing evolving amyloid deposition supported initiation of ATTR-CM therapy. As disease-modifying therapies expand, earlier treatment in high-probability cases could delay worsening of clinical HF.9
Conclusions
We illustrate the coexistence of clinically significant plasma cell dyscrasias with ATTR-CM. These cases underscore the risk of assuming that all patients with a CA phenotype and a concurrent clinically significant plasma cell dyscrasia such as MM or sMM have AL-CM. Given the availability of effective therapies for ATTR-CM and the consequences of delayed treatment initiation, timely and accurate diagnosis is crucial. Additionally, when MGUS is present, noninvasive scintigraphy imaging alone is insufficient for definitive amyloid subtyping, and EMB with mass spectrometry should be performed. Genetic testing serves as an important adjunct, particularly in patients with high-risk features for hereditary ATTR, when EMB is negative, or when unable to be performed in a timely fashion. Ultimately, accurate amyloid subtype classification through interpretation of clinical features, imaging, TTR genetic testing, and mass spectrometry of tissue remains essential to guide prompt diagnosis and initiation of disease-directed therapy in this complex patient population.
Funding Support and Author Disclosures
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
Footnotes
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the Author Center.
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