AL-Amyloidosis, g Light Chain-Related
Guillermo A. Herrera
St. Louis University
St. Louis, MO
Fifty-two year old female with history of hypertension on treatment, fibrocystic breast disease and
carpal tunnel syndrome presented with nephrotic-range proteinuria (6.5 grams per 24 hour collection).
Physical examination was only remarkable for lower extremity edema. Collagen vascular disease work-up
was negative. Laboratory data revealed no evidence of anemia, a BUN of 8 mg/dl and a serum creatinine of
0.7 mg/dL. CBC was normal.
A renal biopsy was performed.
Renal Biopsy Results
Ten glomeruli were identified in the specimen submitted for light microscopic examination.
In the glomeruli, amorphous, eosinophilic, PAS positive hyaline material was identified in mesangial
areas extending into peripheral capillary walls. As a result of the mesangial expansion, the capillary
spaces appeared compressed. The normal mesangial matrix was replaced by the above mentioned material
which was Congo Red and Thioflavin T positive. Apple green birefringence was demonstrated in association
with the Congo Red staining areas. Silver positive spikes were noted protruding laterally from the
replaced mesangial areas. No segmentally or globally sclerosed glomeruli were present. Trichrome stain
showed focal, mild fibrosis associated with tubular atrophy and drop out. Desquamation, fragmentation
and vacuolization of proximal tubular cells was a prominent finding. A few tubular casts were present
but there were no fracture planes in these casts and no reaction of the surrounding interstitium was
noted. Mild thickening of the walls of the arterioles and small sized arteries was additionally
identified. Thioflavin T stain also revealed punctuate fluorescence in the arteriolar walls and Congo
Red stain showed focal apple green birefringence in small vessel walls.
Six glomeruli were seen in the specimen submitted for immunofluorescence studies. Stains
for IgG, IgA, IgM, C3, Clq, fibrinogen, albumin and kappa were negative, as well as the auto-control
section in glomeruli. There was distinctive mesangial and peripheral capillary wall fluorescence for g
light chains. There was also granular staining in proximal tubules for light chains, predominantly l.
Punctate fluorescence was identified along arteriolar and small arterial walls for llight chains. There
was no staining in the interstitium for any of the immunoreactants, including g light chain. The
auto-control section was negative in tubular interstitial and vascular compartments.
Ultrastructurally, there was diffuse, generalized effacement of the foot processes of the
visceral epithelial cells. Aggregates of randomly distributed, non-branching, 8 to 10 mm in diameter
fibrils were identified in subepithelial locations and mesangial areas replacing the normal mesangial
matrix. Along the peripheral capillary walls there was evidence of basement membrane reaction around the
fibrillary aggregates and the same fibrils deposited in the mesangium resulted in marked expansion and
compression of adjacent capillary spaces. Vacuolization, fragmentation and desquamation of proximal
tubular cells was a prominent finding. In addition, the lysosomal system in the proximal tubules
appeared prominent with occasional large and atypical lysosomes noted. No immune complex deposits were
identified in any location. Careful evaluation of the few vessels present in the specimen showed focal
deposits of fibrillary material similar to those previously described.
Diagnosis: AL-Amyloidosis, g light chain-related.
Post Renal Biopsy Clinical Course:
After the diagnosis of AL-amyloidosis was made in the renal biopsy, a serum protein
electrophoresis revealed low IgG and IgM and normal IgA but no monoclonal spikes. Urine protein
electrophoresis demonstrated freeg light chains. A bone marrow aspirate and biopsy revealed 15% plasma
cells with atypical plasma cells confirming the diagnosis of an associated plasma cell myeloma.
The patient was treated with 4 courses of Melphalan and Prednisone with no response. Her
urine protein excretion actually increased to 8 grams in 24 hours collection and the amount of urinary
free g light chains also increased. Her treatment protocol was then changed to VAD (Vincristine,
Adriamycin and Doxarubicin) one year and 8 months after the initial treatment was instituted. She
remained refractory to therapy and renal failure ensued. The patient died two and a half years after the
diagnosis of AL-amyloidosis was made.
This patient presented with nephrotic syndrome and normal renal function. A renal biopsy
was performed to determine the cause of the nephritic syndrome and a diagnosis of amyloidosis is
established. The demonstration of light chain monoclonality (l) in association with the amyloid deposits
established a diagnosis of primary (AL) amyloidosis. Further work-up uncovered a plasma cell dyscrasia
and the patient received treatment using two different chemotherapeutic protocols with poor results.
Clinical and Pathologic Reatures of Al-Amyloidosis
The annual incidence of AL-amyloidosis has been estimated to be 1 per 100,000 individuals
with up to about 2000 new cases diagnosed each year. This disease usually manifests during the
5th to the 6th decade and has a male predominance. Although serum protein
electrophoresis is a good screening test for patients with plasma cell dyscrasias, light chain secreting
and non-secreting myeloma patients generally lack a monoclonal spike in the serum. In a study of 229
patients with AL-amyloidosis in only 40% a monoclonal spike was detected by serum protein electrophoresis
while in 68% of these patients the monoclonal protein was detected by immunoelectrophoresis which is a
more sensitive technique. Because light chains are freely filtered through the glomeruli, examination of
the urine for Bence Jones proteinuria using immunoelectrophoresis and/or immunofixation is important to
support the diagnosis. The urine may have to be significantly concentrated before a monoclonal spike can
be detected. Immunofixation electrophoresis is the most sensitive method to detect monoclonal proteins
in serum and urine samples. A newer effective method to confirm a diagnosis of plasma cell dyscrasia is
to look for free light chains in the serum.
Due to the relative rarity of the disorder and the non-specificity of the clinical
manifestations, AL-amyloidosis is often not recognized as the cause of renal dysfunction until late in
the course of the disease. If there are signs and symptoms suggesting amyloidosis, gingival, rectal or
abdominal pad biopsies may be used for diagnostic purposes. However, currently the diagnosis of
AL-amyloidosis is often made by nephropathologists by demonstrating the presence of amyloidosis in
association with monotypical light chain deposition. g VI represents the most common light chaintype in
these cases. In some cases the pathologist must have a high degree of suspicion to make the correct
diagnosis. The amyloid deposits may be subtle and difficult to confirm using a Congo Red stain which
remains the preferred tinctorial approach to diagnose amyloid. On the contrary, Thioflavin T stain is
much more sensitive and can depict very small amounts of amyloid. Ultrastructural examination can
confirm the diagnosis but occasionally the amyloid deposition is only focal and segmental. The affected
mesangial areas may not be present in the sample submitted for EM or difficult to find. Ultrastructural
immunolabeling may be helpful in these circumstances by highlighting these scattered amyloid deposits.
Ultrastructural criteria for diagnosing amyloid must be strict. When mesangial matrix is
examined at high magnification it may mimic amyloid creating a possible source of confusion. In
fibrillary glomerulopathy the fibrils are much thicker in diameter (approximately 15-20 nm) than
amyloid. Collagen and pre-collagen must also be considered in the differential diagnosis of amyloidosis
by EM; the periodicity of collagen and parallel disposition of precollagen fibrils are of help in
establishing the correct diagnosis. Also in amyloidosis the fibrils colocalize with serum amyloid-P
component. Amyloid deposition can occur in any of the three renal compartments. Vascular amyloid
deposition is usually accompanied by glomerular amyloidosis but there are rare cases in which only
vascular AL-amyloidosis has been demonstrated. Amyloid deposition restricted to the interstitium has not
been documented in the literature.
An important challenge to the recognition of AL-amyloidosis is the fact that the
antibodies to light chains employed in the routine battery of immunofluorescence stains used to evaluate
renal biopsies do not recognize all abnormal light chain proteins; therefore, the amyloid deposits may
not stain for kappa or g light chains suggesting non-AL amyloidosis. Furthermore, the heavy chain (AL)
amyloidosis, although apparently quite rare, also represents a challenge in diagnosis.
A significant number of cases with AL-amyloidosis at the time of initial diagnosis fail to
show evidence of a plasma cell dyscrasia if the bone marrow is examined using routine morphologic
techniques. To identify the underlying plasma cell dyscrasia it is recommended that bone marrow
aspirates be examined by flow cytometry and/or immunohistochemistry to detect he clonal population of
plasma cells. A normal number of plasma cells in the bone marrow does not rule out a diagnosis of
myeloma. The fact that the kidneys are being affected by amyloidogenic light chains is viewed by most as
indirect evidence that there must be an underlying malignant plasma cell disorder. It remains the
responsibility of the pathologist to document that such malignant process is present. Some oncologists
are still reluctant to treat patients with AL-amyloidosis unless unequivocal evidence of myeloma (plasma
cell dyscrasia) is found in the bone marrow specimen, a position that is becoming untenable.
There have been a number of recent advances in the understanding of the pathogenesis of
AL-amyloidosis. Major efforts have been directed towards identifying the primary structural features
(amino acid sequences) that differentiate amyloidogenic from non-amyloidogenic light chains. An in vitro
system of renal amyloidosis has provided very useful information regarding how mesangial cells interact
with monotypical light chains and produce amyloid. Amyloidogenic light chains interact with a yet not
fully characterized receptor on the surface of the mesangial cells. When mesangial cells are incubated
with amyloid producing glomerulopathic light chains a phenotypic change into a macrophage lineage has
been shown to occur. Furthermore, internalization of light chains through a clathrin-mediated mechanism
and lysosomal processing have been demonstrated to play important roles in the process of amyloid
formation. Delivery of amyloidogenic light chains to the mature lysosomal system is a crucial and
integral component of the process of amyloidogenesis.
The in vitro model has depicted crucial steps in this process amenable to possible
therapeutic intervention. The existing in vitro as well as the availability of in vivo experimental
models that duplicate the human form of AL-amyloidosis will provide further insight into the cause and,
ultimately, the effective prevention and treatment of this relentless disease process.
Treatment, Prognosis and Future Expectations
The treatment of patients with AL amyloidosis remains limited. The major therapeutic
efforts are at reducing the amyloid protein precursor-light chains by administration of chemotherapeutic
agents such as Melphalan and Prednisone. Although control of the plasma cell clone can be achieved, the
disease process is rarely reversible and most often renal deterioration occurs. In one randomized
prospective study treatment with these drugs reduced mortality in a group of patients with amyloidosis
compared to a control group receiving Colchicine alone; however, the progression of the renal disease and
incidence of end stage renal disease was not reduced. Even the initial response to treatment in
AL-amyloidosis is limited with one study showing only a 20% response. Restoration of renal function can
be achieved by renal transplantation. In one series, 65% of transplanted patients with amyloidosis (15
of them with AL type) were alive 5 years after transplantation. Systemic complications are responsible
for the majority of the post-transplant morbidity and mortality in these patients. Unfortunately, for
most patients with this condition the overall prognosis is poor and life span limited. Although long
survival has been reported occasionally in AL-amyloidosis, amyloid deposition is usually relentless,
irreversible and fatal 2-3 years after diagnosis. Since currently these cases are being diagnosed
earlier, there is hope that this bleak prognosis may change in the not too distant future.
The fact that the primary sequences of some of the amyloidogenic light chains has been
determined will contribute to the development of pharmacologic compounds that can inhibit or prevent
renal damage in AL-amyloidosis. There are also in vitro and in vivo studies in progress aiming at
determining the mechanisms responsible for the localization of amyloid deposits to particular organs and
identifying cellular or humoral factors that can accelerate or slow down amyloid deposition. We are
currently working with an animal model of AL-amyloidogenesis which will hopefully allow testing of
various therapeutic maneuvers to control, ameliorate or reverse renal amyloidosis.
- Bellotti, V., Mangione, P., Merlini, Giampaolo. Immunoglobulin light chain amyloidosis-the archetype of structural and pathogenic variability. J Struct Bio 130:280-289, 2000.
- Buxbaum, J.: Aberrant immunoglobulin synthesis light chain amyloidosis. J Clin Invest 78:798-806, 1986
- Buxbaum, J.N., Hurley, M.E., Chuba, J., Spiro, T.: Amyloidosis of the AL type. Clinical, morphological and biochemical aspects of the response to therapy with alkylating agents and prednisone. Am. J. Med. 67:867-878, 1979
- Cogne, M., Silvain, C., Khamlichi, A.A., Preud'Homme, J.L. Structurally abnormal immunoglobulins in human immunoproliferative disorders. Blood 79:2181-2195, 1992
- Eulitz M., Weiss DT, Solomon A. Immunoglobulin heavy-chain-associated amyloidosis. Proc Natl Acad Sci 87:6542-6546, 1990
- Gallo, G., Picken, M., Buxbaum, J., Frangione, B. The spectrum of monoclonal immunoglobulin deposition disease associated with immunocytic dyscrasias. Semin Hematol 26:234-245, 1989
- Gise, H., Christ, H., Bohle, A.: Early glomerular lesions in amyloidosis. Virchowx Arch. [A] 390:259-272, 1981
- Herrera, G.A., Sanders, P.W., Reddy, B.V.et al: Ultrastructural immunolabeling: A unique diagnostic tool in monoclonal light chain related renal diseases. Ultrastruct Pathol 17:93-113,1993
- Herrera, G.A.: Renal manifestations in plasma cell dyscrasias: an appraisal from the patient's bedside to the research laboratory. Annals Diagn Pathol 4:174-200, 2000.
- Herrera, G.A., Russell, W.J., Isaac, J.et al: Glomerulopathic light chain – mesangial cell interactions modulate in vitro extracellular matrix remodeling and reproduce mesangiopathic findings documented in vivo. Ultrastruct Pathol 23:107-126, 1999.
- Isaac, J., Herrera, G.A.: Renal biopsy as a primary diagnostic tool in plasma cell dyscrasias. Pathol. Case Rev 3:183-189, 1998
- Kyle, R.A., Geipp, P.R.: Amyloidosis (AL): Clinical and laboratory features in 229 patients. Mayo Clin. Proc. 58:665-683, 1983
- Kyle, R.A., Gertz, M.A.: Primary systemic amyloidosis: clinical and laboratory features in 474 cases. Semin Hematol. 32:45-59, 1995
- Merlini G, Bellotti V. Mechanisms of disease: Molecular mechanisms of amyloidosis 349:583-596, 2003
- Sammett, D., Dagher, F., Abbi, R.et al: Renal transplantation in multiple myeloma. Transplantation 62:1577-1580, 1996
- Sanders, P.W., Herrera, G.A.: Monoclonal immunoglobulin light chain-related renal diseases. Sem. Nephrol. 13:324-341, 1993
- Sanders, P.W., Herrera, G.A., Galla, J.H., Lott, R.L.: Morphologic alterations of the proximal tubules of patients with light chain related renal disease. Kidney Intl. 33:881-889, 1988
- Shirahama, T., Cohen, A.S.: Intralysosomal formation of amyloid fibrils. Am. J. Pathol. 81:101-109, 1975
- Solomon, A., Frangione, B., Franklin, E.C.: Bence Jones proteins and light chains of immunoglobulins. Preferential association of the lambda VI subgroup of human light chains with amyloidosis (AL) lambda. J. Clin. Invest. 70:453-460, 1982
- Solomon, A., Weiss, D.T., Kattine, A.A.: Nephrotoxic potential of Bence Jones proteins. N. Engl J Med 324:1845-1851, 1991.
- Solomon, A., Weiss, D.T.: Protein and host factors implicated in the pathogenesis of light chain amyloidosis (AL amyloidosis). Amyloid: Int. J. Exp. Clin. Invest. 2:269-279, 1995
- Tagouri, Y.M., Sanders, P.W., Picken, M.M.et al: In vitro AL-amyloid formation by rat and human mesangial cells. Lab. Invest. 74:290-302, 1996
- Teilum, G. Pathogenesis of Amyloidosis: The two-phase cellular theory of local secretion. Acta Path et Microbiol, Scandinav 61:21-45, 1964
- Teng J, Russell WJ, Xin G et al. Different types of glomerulopathic light chains interact with mesangial cells using a common receptor but exhibit different intracellular trafficking patterns. Lab Invest 84:440-451, 2004