Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (380 page)

   
Serum protein electrophoresis and immunofixation
reveal a monoclonal protein (κ or λ) and identify a specific heavy chain.

   
Urine protein electrophoresis and immunofixation
reveal M protein.

   
Serum free light chain immunoassay
. Abnormal κ-to-λ ratio may be seen.

   
Renal function tests
may be abnormal in cases with monoclonal light chain proteinuria.

   
Immunophenotype
: Bright CD38 and/or CD138 with monoclonal cytoplasmic κ or λ is usually observed. Contrary to PCM, CD56 staining is rarely observed. CD19 and/or CD20 is frequently absent.

   
Cytogenetics
: Abnormal karyotypes (similar to PCM) are frequently found, and there is a higher incidence of unfavorable cytogenetics—del 13q14, t(4;14)(p16.3;q32), t(14;16)(q32;q23), and del 17p13.

Suggested Reading

Swerdlow SH, Campo E, Harris NL, et al.
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues
, 4th ed. Lyon, France: International Agency for Research on Cancer; 2008:203.

MONOCLONAL LIGHT AND HEAVY CHAIN DEPOSITION DISEASES

   Definition

These disorders include light chain deposition disease (LCDD), heavy chain deposition disease (HCDD), and light and heavy chain deposition disease (LHCDD). They are seen in the context of plasma cell disorders or of lymphomas with plasmacytic differentiation. There is abnormal deposition of light chain, heavy chain, or both light and heavy chains in tissues, but in contrast to amyloidosis, they do not form β sheets and do not stain with Congo red. Median survival is 4 years.

   Who Should Be Suspected?

Middle-aged (median age 56 years) male patients with symptoms of Ig deposition in various organs: the kidney (nephrotic syndrome and renal failure), heart, liver, peripheral nerves, lungs, blood vessels, and joints.

   Laboratory Findings

   
Bone marrow biopsy and aspirate
: Evidence of plasmacytosis, overt PCM, lymphoplasmacytic lymphoma, or marginal zone lymphoma may be present.

   
Tissue biopsy of involved organs
(e.g., heart, kidneys, liver) shows evidence of nonamyloid, nonfibrillary, amorphous eosinophilic material. LCCD is diagnosed by renal biopsy, showing nodular sclerosing glomerulopathy by light microscopy, diffuse linear staining of glomerular and tubular basement membrane κ or λ light chains by immunofluorescence, and nonfibrillar electron-dense deposits by electron microscopy. The deposits must be Congo red negative.

   
CBC
is usually normal. Rouleaux formation (due to paraproteinemia) may be seen.