paraproteins and the kidney

Arun Chawla, MD

Group of diseases characterized by clonal expansion of abnormal plasma cells

Clonal expansion results in overproduction of a monoclonal M protein - could be either a whole immunoglobulin or a fragment(heavy or light chain)

IgG – 52%, IgA – 21% and IgM in 12% and light chains alone in 11%.

Rarely nonsecretory (3%)

Collectively referred to as monoclonal gammopathies.

Copyright ©2010 American Society of Hematology. Copyright restrictions may apply.

Ghobrial, I. M. et al. ASH-SAP 2010;2010:581-604

Table 20-1 Diagnostic criteria for monoclonal gammopathies

A normal Ig is composed of two LCs and two HCs.

LCs and HCs are themselves made up of so-called constant (C) and variable (V) globular domains.

Limited number of genes encode the constant region.

Multiple gene segments are rearranged to produce a variable domain unique to each chain. Diversity is further amplified by mutations and variations of the linking peptide segment.Although LCs (and HCs) have many structural similarities, they

also possess a unique sequence that may be responsible for physicochemical peculiarities, hence their deposition in tissue or interaction with tissue constituents. Biochemical studies have identified specific Ig structural abnormalities that are associated with MM, MIDD, and amyloidosis -

Second most common hematological malignancy

Males to female 3:2

Incidence doubled in African- Americans and Pacific Islanders compared with Caucasians

Most imp risk factor preceding MGUS – present in 5% of population > 70 years

More risk of transformation with IgA paraproteins than with IgG or IgM

Incidence is 4.3 per 100,000 people, but the incidence ranges from 1 per 100,000 for people who are 40 to 49 yr of age to 49 per 100,000 population for >80 yr.

Role of abberant class switch recombination

Molecular deletions of chromosome 13q in upto 80% of myeloma cases

Environmental factors like ionizing radiation, farming & petrochemicals occupation, engine exhaust and hair dyes might increase the risk

Cells localize in marrow with interaction of cell adhesion molecules and their ligands in BMSCs & matrix proteins

BMScs also produce Il-6 and VEGF (autocrine loops)Il-6 is both a product and growth factor for myeloma cells and correlate

with greater tumor mass & outcome; with normal levels in smouldering disease

So is VEGF and CRP (stimulated by IL-6 stimulation of hepatocytes) Il-1β elevated in 95% of myeloma but <25% of MGUS

•Plasma cells normally produce more light chains than heavy chains.

•lambda chains dimerize and are less freely excreted. The normal rate of light chain excretion is less than 30 mg/day.

• Light chains are not detected by the urinary dipstick, which primarily senses albumin.

• urine should be tested with sulfosalicylic acid in any patient suspected to have myeloma

Filtered light chains are endocytosed by the PCT cells via the tandem scavenger receptor system cubilin/megalin

Endocytosed through the clathrin dependent

endosomal/lysosomal pathway

LCs incorporated in endosomes that fuse with primary lysosomes where proteases, mainly cathepsin B, degrade the proteins into amino acids, which are returned to the circulation by the baso-lateral route .

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Physiology

Due to overproduction, increase glomerular permeability or a decrease reabsorption due to PT cell injury there is an increase in light chain excretion that can range from 100 mg to more than 20 grams per day

Excessive filtered load exceeds catabolic reserve and leads to release of lysosomal contents into cytoplasm which activates NFκB which promotes synthesis of IL-6 therby activating signaling pathways causing interstitial inflammation & fibrosis.

Rarely, Fanconi’s syndrome develops when partially digested chains serve as a nidus for crystals in PT endosomes which interfere with apical membrane transportetrs.

>50% of cases diagnosed with myeloma

Reversible in most cases but 10% require acute HD

ESRD incidence due to myeloma is 1%

mutations in the Ig molecule are the basis for the discrete pathologic lesions that are seen in multiple myeloma – cast nephropathy occurring in up to 55%, Ig lightchain-associated disease with amyloidosis in 30%, LCDD in 19%, and int nephritis and ATN (light chain dose dependent toxicity to PT cell) in over 10% of patients.

Tubular functional abnormalities Fanconi syndrome Concentrating defect - NDI Distal renal tubular acidosis ProteinuriaStructural abnormalities “Myeloma kidney” (chronic tubulointerstitial nephropathy) Acute cast nephropathy Glomerulopathy Light chain deposition disease Amyloidosis, type AL Cryoglobulinemic glomerulonephritis Fibrillary (monotypical membranous) glomerulonephritis Proliferative glomerulonephritis with monoclonal Ig deposits

(MIDD) Vascular lesions Neoplastic cell infiltrationOthers (miscellaneous) Dehydration, contrast media and ACE i–induced renal failure Acute uric acid nephropathy Obstructive nephropathy Hyperviscosity syndrome

The casts contain either Ig light chain (cationic), Ig, and Tamm-Horsfall glycoprotein (anionic) therby causing distal obstruction.

In H&E-stained sections, the casts are intensely eosinophilic, and they seem “brittle” because they are lamellated and fractured frequently during histological processing. Often are surrounded by macrophages and giant cells

Casts are associated with tubular rupture causing Ch Int Nephritis.

Protein cast obstructs tubule with syncitial giant cell reaction around it

The extent of cast formation does not parallel the degree of interstitial fibrosis and tubular atrophy;

renal function correlates with interstitial fibrosis and tubular atrophy, not with cast formation

Affinity of light chains to complex with THP proteins is also determined by aminoacids in CDR region which can be increased by volume depletion, acidic environment, reduced tubule flow rates and raised tubule calcium & chloride (& hence furosemide!). Radiocontrast – renal vasoconstriction and direct tubular toxicity.

Myeloma cast nephropathy demonstrating light-chain restriction in the casts.


Korbet, S. M. et al. J Am Soc Nephrol 2006;17:2533-2545

The cast stained with Ig light chain κ (A) shows bright (3+) staining.

The same cast stained in a serial section for light chain λ (B) is negative.

Bone pain – 65-70%Anemia – 60-65%Renal Failure – 55%Proteinuria – almost 90%M-band - 76%Hepatomegaly – 20%

Elevated BUN/crHypercalcemiaWhat about Anion gap?? (reduced if

paraprotein carries a positive charge (cationic as in IgG)

USG to show nl sized kidneys with increased echogenicity due to tubular proteinaceous casts and associated Int Nephritis.

identify FLCs at a minimum concentration of 100-150mg/l.Insufficient to identify non secretory or oligo-secretory myeloma

Technique uses purified polyclonal antibodies against free k and λ light chains which are precoated to latex particles and then analyzed by nephlometric assay for quantification. Permits detection of light chain to a level of 2-4mg/l.

Sera from patients with either polyclonal hypergammaglobulinemia or renal impairment often have elevated k FLC and λ FLC due to increased synthesis or reduced renal clearance. The k/λFLC ratio (rFLC), however, usually remains normal.

FLC k/λ 0.26–1.65. If > 1.65 κ clonal expansion and if < 0.26 evidence of clonal expansion producing λ chains.

specificity of the test is 100%, with a sensitivity of 97% when combine with SPEP and sIFE.

If a patient has an infection or a rheumatologic condition, the test should be repeated at a later date.

Also used to monitor disease course and response to treatment in PCDs

concentration was overestimated in 75% of cases.

In another study, correlation between concentrations of FLC in serum and urine measured by immunoassay in 224 patients was non- existent.

The urine immunoglobulin FLC test is NOT recommended for monitoring patients.

Median survival 62 mo



High dose steroidsThalidomide/Lenalidomide – inhibhits VEGF, IL-6

and reduces stromal molecules expressionCombination of

melphalan/dexamethasone/thalidomideFor transplant candidates –

bortezomib/dexa/thalidomideSecond gen proteosome inhibhitors and Anti IL-6

monoclonal antibodyRadiotherapy in pts with extensive lytic lesions and

bone painAutologous stem cell transplant

EUROPEAN JOURNAL OF CANCER 4 2 ( 2 0 0 6 )

Leung et al. KI (2008)

Restoration of intravascular volume

Treat hypercalcemia with volume repletion , loop diuretics and cautious use of bisphosphonates

Pamidronate 30mg i.v if GFR<10ml/min. Asso with collapsing FSGS. Zolendronate not recommended with advanced renal failure as associated with ATN.

Alkalinization of urine?? Vs. Normal saline

Discontinuing NSAIDS and avoiding use of intravenous contrast agents

FLC have a large volume of distribution and rapid plasma refilling after plasma exchange. Only 15% -20% sFLCs are exchanged with one plasma volume.

Although small studies earlier demonstrated benefit in terms of renal recovery and pt survival; the same was not reproduced in a RCT.

Argument is if carefully selected biopsy proven cases of CN treated with plasma exchange to reduce sFLC by >50%, renal recovery and dialysis independence is enhanced significantly

Pts got PD in control and HD in PPx group

Eleven patients were randomized to receive PLEX. They noted no differences in the overall renal recovery rate however, in a subgroup analysis of the dialysis patients, renal recovery occurred only in those who received PLEX. Small study.

compromised by the use of a composite outcome which disadvantaged PLEX because patient who died with improved renal function and those with eGFR <30 were considered failures. the renal pathology was not verified due to the low biopsy rate. Finally, no method was employed to assess the adequacy of treatment.

new hemodialysis membrane (HCO 1100) that removes the circulating light chains more efficiently has been recently developed

Small study investigating hemodialysis with a protein-leaking dialyzer indicated that large reductions in the concentration of serum-free light chains could be obtained.

Need further confirmation in larger studies – EuLite trial – results awaited.

historically not been eligible for a kidney transplant because of their malignancy; conversely, allogeneic stem-cell transplants, the only known curative treatment for multiple myeloma, have rarely been performed in patients with ESRD because of prohibitive morbidity and mortality risks.

patients without extrarenal manifestations of myeloma for 1 yr, transplantation has been successful and may prove to be an alternative to dialysis.

The successful use of ASCT in dialysis-dependent patients with myeloma may increase the potential for renal transplantation in these patients.

seven patients (median age: 48 years [range: 34–55 years]) with MM & ESRD underwent a combined HLA-matched kidney and bone marrow transplant with lead follow-up time > 12 years.

Preparative therapy consisted of high-dose cyclophosphamide, thymoglobulin and thymic irradiation. Cyclosporine as the sole posttransplant immunosuppressive therapy was tapered and discontinued as early as day 73 posttransplant.

Five of seven patients are alive, 4 with no evidence of myeloma from 4 to 12.1 years post-transplant. Three patients have normal or near-normal renal function without needing systemic immunosuppression.

Known as primary systemic amyloidosis

Usually caused by monoclonal light chain (AL) with λ : k ratio of 2-3:1.

Rarely by monoclonal heavy chain(AH)

Incidence 9 per million per yr with median age 64 yrs.

AL amyloid accounts for 10% of nephrotic syndrome in adults over 44 years of age.

Proteinuria- presentation in 65% of patients, can be massive >20g

Renal insufficiency- half present with reduced renal function, 20% have Scr>2mg/dl

Hypotension (adrenal)- in previously hypertensives, orthostatic from autonomic neuropathy

20% meet criteria for MM, Lambda>kappa(2:1)

Note : Formation of amyloid fibrils is influenced by AA sequences in light chain variable regions & the degree of enzymatic glycosylation

Cardiac- CHF, conduction defects, arrythmia, Restrictive cardiomyopathy.

GI –diarrhea, GI bleed, malabsorption and obstruction

Nervous system- peripheral neuropathy, autonomic dysfunction, carpal tunnel.

Hepatic- enlarged liver, elevated liver enzymes

Skin – infiltrative plaques & nodules, gen bruising

Vascular infiltaration leads to bleeding complications, Factor X deficiency

Demonstration of Congo red positive nonbranching amyloid fibrils that have an antiparallel beta-pleated sheet configuration in tissues (fat pad, skin, b.m.)

sFLC combined with “conventional assays” permits diagnosis in 99% of cases. (conventional alone <90%)

sFLC also informs of severity of organ involvement and is of prognostic value

Immunostaining of bone marrow biopsy for λ and κ shows clonal plasma cells even when SPEP/UPEP negative (10%) and will help to exclude underlying myeloma

Mesangial & Cap loops amyloid deposits. Arteriolar wall with amyloid.

www.pathology.vcu.edu


IMMUNOHISTOCHEMICAL STAININGS To differentiate amyloid AL and AA, specific antibodies can also be used.


randomly arranged, nonbranching fibrils with an average diameter of 90 to 110 Å

Renal amyloidosis, ultrastructural appearance


Amyloid p glycoprotein component present in basement membrane binds the amyloid fibrils

The median survival in patients with AL-amyloidosis and nephrotic syndrome is 16 mo (with chemo alone)

λ light chains have a poorer prognosis than patients with κ light chains (12 versus 30 mo median survival)

Patients who present with a serum creatinine 1.3 mg/dl had a median survival of 15 mo, compared with 26 mo (P 0.007) for patients with normal renal function

50% of deaths due to cardiac involvement & 18% progress to ESRD

Gertz et al. Am J Clin Path 1990

Treatment

Stem cell transplant - 4 yr was significantly better in patients who received ASCT compared with standard chemotherapy (71% versus 41%;P 0.001)

Current HematologicMalignancy Reports 2009, 4:91–98

1-yr mortality rate on dialysis of 44% for patients with Al amyloidosis, compared with 22% of all ESRD patients, is surpassed only by myeloma cast nephropathy (49%) and AIDS nephropathy (45%)

successful ASCT may allow more patients with

AL-amyloidosis the opportunity for renal transplantation.

For nephrologists – to manage nephrotic syndrome, orthsostatic hypotension and volume status

Selection criteria for renal transplantation included ESRD, age under 70 years, absence of myeloma or extensive extrarenal amyloidosis, ECOG performance status of 1 or 2.

The median patient survival of 6.5 years from renal transplantation

Light chain deposition disease (most common > 75%)Light and heavy chain deposition disease (<10%)Heavy chain deposition disease (γ chain & <20%)MIDD with cast nephropathy (20%)MIDD with amyloidosis

Renal insufficiencyNephrotic range proteinuria in 40% with dipstick positiveHypertensionExtra renal manifestations in 35%- CHF, liver enzyme

elevation, peripheral neuropathy, muscle wasting, carpal tunnel syndrome, psychosis

35% - 65% meet criteria for Multiple myelomaPredominantly Kappa light chains(3:1)

Light microscopy- mesangial expansion, nodular sclerosis, thickening of the GBM. MPGN and has also been reported, interstitial nephritis and Congo red negative.

Immunoflorescence- linear staining of TBM with light chain antisera, staining may be weak or absent with nodules.

Electron Microscopy- granular electron dense deposits in the sub epithelial, endothelial and focal mesangial.


Korbet, S. M. et al. J Am Soc Nephrol 2006;17:2533-2545

MIDD showing light chain restriction by immunofluorescence microscopy

inconstant electron-dense, subendothelial, granular, punctuate deposits that may diffusely infiltrate the basal lamina.

Renal –median time to ESRD is 2.7 years.

Multiple myeloma, coexistent cast nephropathy and high presenting serum creatinine predict progression to ESRD

Patient survival varies from 18 months to 5 years

Survival related to presence of multiple myeloma.

Renal limited disease - ESRD – no cytotoxic therapy. renal transplant not an

option unless there is hematologic remission. - Non ESRD : Anti-myeloma therapy reasonable with a

goal of stopping renal damage

Extra renal disease or myeloma- Chemotherapy , stem cell transplant.

Cryoglobulemia in Plasma Cell diseaseFibrillary GNImmunotactoid GNProximal Tubulopathies

paraproteins and the kidney

Education

ig light chain

light chain

tubular atrophy

cast stained

light chains

interstitial

int nephritis

casts