Systemic AL Amyloidosis with Cardiac and Renal Involvement

Andrew Bland, MD, FACP, FAAP

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1. Case Presentation

Admission Data

Subsequent Evaluation

Test	Value	Significance
Free light chain kappa	17.4 mg/dL (= 174 mg/L)	~9x upper limit of normal
Free light chain lambda	3.24 mg/dL (= 32.4 mg/L)	Mildly elevated (CKD artifact)
Kappa/Lambda ratio	5.37	Above renal-adjusted ULN of 3.1
Echocardiogram	EF 45%, LVH, impaired relaxation	Grade I-II diastolic dysfunction
BNP	4,598 pg/mL	Markedly elevated
Troponin I	59 ng/L	Above cardiac threshold

2. Proteinuria Phenotyping -- Glomerular Disease, Not Cast Nephropathy

The urine protein/Cr of 7.9 with albumin/Cr >4 establishes that the proteinuria is albumin-predominant and glomerular in origin. This is the first and most diagnostically decisive point in the case.

Feature	Cast Nephropathy (Myeloma Kidney)	Glomerular Amyloid / LCDD
Primary pathology	Distal tubular casts	Mesangial/GBM fibril or non-fibrillar deposits
Proteinuria type	Bence Jones (light chains)	Albumin-dominant
Urine dipstick	Trace or negative (misses light chains)	3-4+ positive
Serum albumin	Usually preserved	Low -- hypoalbuminemia
FLC threshold	Typically >500-1,500 mg/L	Often lower (<500 mg/L)
Volume physiology	Variable	Oncotic-driven underfilling

3. Free Light Chain Interpretation in Renal Failure

3.1 Unit Conversion -- A Critical Potential Error Source

Serum free light chains are measured and reported in mg/L at most reference laboratories. When values are reported in mg/dL (as in this case), conversion is mandatory: 1 mg/dL = 10 mg/L

Analyte	Reported (mg/dL)	Converted (mg/L)	Standard Reference (mg/L)
Kappa	17.4	174	3.3-19.4
Lambda	3.24	32.4	5.7-26.3
Ratio	5.37		0.26-1.65

3.2 Renal-Adjusted Reference Range

The standard FLC reference range (0.26-1.65) was established in patients with normal renal function. The extended reference range for renal impairment is approximately 0.37-3.1. This patient's ratio of 5.37 exceeds the renal-adjusted upper limit, confirming a true clonal process rather than a CKD artifact.

3.3 Delta FLC (dFLC) Calculation

4. Differential Diagnosis -- Kappa-Dominant FLC Pattern

The kappa-dominant FLC pattern changes the differential hierarchy compared to a lambda-dominant presentation. Lambda accounts for approximately 70-75% of AL amyloidosis cases, while kappa predominates in multiple myeloma (approximately 60-65%).

1. Light Chain Deposition Disease (LCDD) -- Leading Diagnosis

LCDD most commonly involves kappa light chains (approximately 60-70% of LCDD cases), producing a non-fibrillar, Congo red-negative glomerular deposit along the GBM and mesangium. Presentation is nephrotic-range albuminuria with preserved or mildly reduced GFR and absent CRAB features -- precisely this patient's profile.

2. Kappa AL Amyloidosis -- Close Second

Kappa AL amyloidosis accounts for approximately 25-30% of AL cases. Congo red staining of kidney biopsy will be positive with apple-green birefringence under polarized light if this is the diagnosis.

3. MGRS-class Disease -- Broadest Category

Either of the above may represent a Monoclonal Gammopathy of Renal Significance (MGRS) -- renal disease caused by a clonal immunoglobulin that does not meet criteria for overt myeloma.

SLiM Criteria Assessment

The involved/uninvolved FLC ratio criterion for a myeloma-defining biomarker event requires ≥100 (kappa direction). This patient's ratio of 5.37 does not meet that threshold. This does not diminish the urgency of evaluation; MGRS-class disease causes dialysis-driving renal failure from clones that by definition do not qualify as myeloma.

5. Cardiac Evaluation -- Confirmed Advanced Involvement

5.1 Biomarker Staging

Measured finding	Value	Interpretation
BNP	4,598 pg/mL	Markedly elevated; not numerically interchangeable with NT-proBNP
High-sensitivity troponin I	59 ng/L	Interpret with the exact assay and validated staging system
Formal cardiac stage	Not established here	Confirm diagnosis and required biomarkers before assigning a stage

The reported BNP and high-sensitivity troponin I indicate a concerning cardiac phenotype but are not interchangeable with the NT-proBNP and specified troponin assays of another staging system. Confirm amyloid diagnosis and apply a validated assay-specific scheme before assigning a stage or stage-based prognosis. CKD also affects biomarker interpretation.

5.2 Echocardiographic Reinterpretation

The echocardiogram showing EF 45%, LVH, and impaired relaxation was initially framed as hypertensive heart disease. The biomarker and hemodynamic findings warrant reassessment for infiltrative and other causes; a formal stage remains unconfirmed:

• EF 45% in cardiac amyloidosis does not represent mild systolic dysfunction -- it represents the transition point where systolic reserve is becoming exhausted
• "LVH" in amyloidosis is infiltrative pseudohypertrophy -- amyloid fibrils depositing in the myocardial interstitium, not true myocyte hypertrophy
• The echo should be re-read with a dedicated amyloid protocol including global longitudinal strain (GLS) with apical sparing pattern

6. Renal Staging (Palladini 2014 System)

Risk Factor	Patient Status
eGFR <50 mL/min/1.73m2	YES -- Cr 4.0, eGFR estimated 15-20 mL/min
Proteinuria >5 g/day	YES -- Protein/Cr 7.9, consistent with >15-20 g/day
Renal Stage	Stage III (both adverse criteria present)

If AL amyloidosis is confirmed, cardiac and renal risk must be staged separately using each system’s required measurements. Patients with Palladini Renal Stage III have a 60-85% probability of requiring dialysis within 3 years.

7. The Diuresis Problem -- Cardiorenal Physiology of Amyloidosis

Why Diuresis Failed

Creatinine rising from 2.5 to 4.0 during aggressive loop diuretic therapy with minimal fluid removal is the pathognomonic hemodynamic signature of advanced cardiorenal amyloidosis:

1. Oncotic failure: With albumin at 3.1 g/dL, plasma oncotic pressure is insufficient to draw interstitial edema fluid back into the intravascular compartment
2. Stiff ventricle dependence on preload: The amyloid-infiltrated LV requires elevated filling pressures to maintain stroke volume; diuresis drops cardiac output, reducing renal perfusion
3. Tubular light chain toxicity: Loop diuretics concentrate tubular fluid, potentially increasing tubular light chain concentration and promoting Tamm-Horsfall protein binding

8. Tissue Diagnosis -- Required, Not Optional

Kidney biopsy is necessary to differentiate between entities with identical laboratory profiles but distinct pathology:

Finding	AL Amyloidosis	LCDD
Congo red stain	Positive -- apple-green birefringence	Negative
Electron microscopy	Fibrils 8-12 nm, randomly arranged	Non-fibrillar, organized, granular deposits
Immunofluorescence	Restricted light chain (Congo red confirms fibril)	Linear kappa or lambda staining along GBM
Mass spectrometry amyloid typing	Required -- confirms AL vs. AA vs. ATTR	N/A
Treatment implication	Dara-VCd	Clone-directed therapy (similar but biopsy defines urgency)

Abdominal fat pad biopsy is a less invasive alternative with approximately 60-80% sensitivity for systemic AL amyloidosis. Bone marrow biopsy is required for clone characterization, cytogenetics, and assessment of plasma cell percentage.

9. Treatment Framework

Standard of Care: Dara-VCd

The ANDROMEDA phase 3 trial established Dara-VCd as the first FDA-approved therapy for newly diagnosed AL amyloidosis. In 388 patients, daratumumab addition to VCd resulted in a hematologic complete response rate of 53.3% versus 18.1% with significantly superior survival free from major organ deterioration.

Three Pillars of Outcome Improvement

Supportive Care Considerations

• Diuresis: Hold or dramatically reduce; if volume management is mandatory, consider ultrafiltration after RHC-guided hemodynamic assessment
• Albumin infusions: Physiologically intuitive but not proven to improve outcomes; may precipitate pulmonary edema -- use with caution
• Avoid: ACE inhibitors, ARBs, beta-blockers, non-DHP calcium channel blockers
• Coagulopathy surveillance: Factor X level, CBC, INR before procedures
• Renal support: If creatinine continues to rise, early renal replacement therapy planning should begin

10. Priority Diagnostic and Management Checklist

11. Summary

This case represents systemic AL amyloidosis (or LCDD -- tissue biopsy will distinguish) with confirmed multi-organ involvement. The key diagnostic milestones and their clinical implications:

1. The proteinuria phenotype (albumin/Cr >4, protein/Cr 7.9, hypoalbuminemia, 3+ edema) established glomerular disease and excluded cast nephropathy as the primary lesion
2. The kappa FLC of 174 mg/L with ratio 5.37 above the renal-adjusted reference range confirmed a clonal kappa-dominant plasma cell dyscrasia
3. The albumin-rich proteinuria, abnormal free-light-chain ratio, kidney decline, and severe cardiac findings warrant urgent coordinated evaluation. They do not by themselves establish amyloid type or a validated Mayo cardiac stage. Complete serum/urine immunofixation, tissue diagnosis and typing when indicated, and the exact biomarkers required for the selected staging system. Manage congestion and perfusion while hematology, cardiology, and nephrology clarify the cause.
4. The combination of absent CRAB features with glomerular nephrotic syndrome and a small-to-moderate kappa clone makes LCDD the leading tissue diagnosis, with kappa AL amyloidosis as a close alternative -- only the kidney biopsy resolves this
5. The diuresis failure reflects the hemodynamic paradox of the amyloid cardiorenal phenotype: simultaneous total body volume overload and intravascular depletion from oncotic failure and a stiff, preload-dependent ventricle
6. Multidisciplinary emergent care coordination is the clinical priority

References

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