Microscopic description:

Sections of cardiac muscle with diffuse deposition of amorphous eosinophilic material, surrounded by foreign body giant cell reaction and intimately associated with a prominent lymphoplasmacytic infiltrate. The majority of the infiltrate was composed of mature plasma cells with Dutcher bodies admixed with far a fewer number of small lymphocytes with condensed chromatin that formed small lymphocytic aggregates. Areas of necrosis with focal osseous metaplasia were seen.

Congo red stain came out to be negative. No amyloid deposition was noted.

Although there was a minimal associated lymphoid component with the population of kappa light chain restricted plasma cells, the predominant expression of CD19 and CD45 by abnormally proliferated monotypic plasma cells was suggestive of low-grade B cell lymphoma with extensive plasmacytic differentiation, such as marginal zone lymphoma with plasmacytic differentiation and lymphoplasmacytic lymphoma.

Discussion:

Light chain deposition disease (LCDD) also known as Non-Amyloidotic Immunoglobulin Deposition Disease (NIDD) is a rare systemic disorder characterized by the abnormal clonal proliferation of B lymphocytes and plasma cells that causes a significant synthesis of monotypical immunoglobulin light chains, usually kappa 1 with deposition in multiple organs.

The light chains are Congophobic (often Thiboflavine-T positive) and usually have a fine granular ultrastructure as seen under an electron microscope, compared to the fibrillar pattern in amyloidosis.

The structural configuration of the free light chains makes them water soluble, smoothly filtering across the glomeruli and getting reabsorbed by the tubular cells. As a result kidneys are the most commonly involved organs, but not an essential criterion for making the diagnosis.

Among the extra-renal manifestations, cardiac involvement (Cardiac Non-amyloidotic Immunoglobulin Deposition Disease – CIDD) is one of the most frequent, ranging from 20 to 50% of cases.2 

The free immunoglobulin gets deposited in the cardiac wall muscles in discontinuous layers adjacent to the plasma membranes of cardiac myocytes, arteriolar endothelial and smooth muscle cells, and neural elements.3

Patients with CIDD, present with heart failure, cardiomyopathy, arrhythmias, myocardial infarction, etc. Atrial mass presentation, is one of its own kind.

Though no specific treatment is available for CIDD, it is seen that cardiac functions return to normal with remission of the underlying lymphoproliferative disease or plasma dyscrasia.4

References:

Mohan, M., et al., A Case of Cardiac Light Chain Deposition Disease in a Patient with Solitary Plasmacytoma. Am J Case Rep, 2016. 17: p. 173-6.

Buxbaum, J.N., et al., Monoclonal immunoglobulin deposition disease: light chain and light and heavy chain deposition diseases and their relation to light chain amyloidosis. Clinical features, immunopathology, and molecular analysis. Ann Intern Med, 1990. 112(6): p. 455-64.

McAllister, H.A., Jr., et al., Restrictive cardiomyopathy with kappa light chain deposits in myocardium as a complication of multiple myeloma. Histochemical and electron microscopic observations. Arch Pathol Lab Med, 1988. 112(11): p. 1151-4.

Schattner, A., et al., Case report: multiple myeloma presenting as a diastolic heart failure with no evidence of amyloidosis. Am J Med Sci, 1995. 310(6): p. 256-7.

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