Mini-Review

Leukocyte Cell–Derived Chemotaxin 2–Associated : A Recently Recognized Disease with Distinct Clinicopathologic Characteristics

Samih H. Nasr,* Ahmet Dogan,† and Christopher P. Larsen‡

Abstract *Department of Amyloidosis derived from leukocyte cell–derived chemotaxin 2 is a recently recognized form of amyloidosis, and Laboratory Medicine it has already been established as a frequent form of systemic amyloidosis in the United States, with predominant and Pathology, Mayo involvement of kidney and liver. The disease has a strong ethnic bias, affecting mainly Hispanics (particularly Clinic, Rochester, Minnesota; Mexicans). Additional ethnic groups prone to develop amyloidosis derived from leukocyte cell–derived chemo- † taxin 2 include Punjabis, First Nations people in British Columbia, and Native Americans. Most patients are elderly Department of Pathology, Memorial who present with chronic renal insufficiency and bland urinary sediment. is variable, being absent Sloan-Kettering altogether in about one third of patients. Liver involvement is frequently an incidental finding. Amyloidosis de- Cancer Center, New rived from leukocyte cell–derived chemotaxin 2 deposits shows a characteristic distribution: in the kidney, there is York, New York; and ‡ consistent involvement of cortical interstitium, whereas in the liver, there is a preferential involvement of peri- Nephropath, Little Rock, Arkansas portal and pericentral vein regions. Concurrent renal disease is frequent, with diabetic nephropathy and IgA nephropathy being the most common. Patient survival is excellent, likely because of the rarity of cardiac in- Correspondence: volvement, whereas renal survival is guarded, with a median renal survival of 62 months in those without Dr. Samih H. Nasr, concurrent renal disease. There is currently no efficacious therapy for amyloidosis derived from leukocyte Mayo Clinic, Division cell–derived chemotaxin 2 amyloidosis. Renal transplantation seems to be a reasonable treatment for patients of Anatomic Pathology, with advanced renal failure, although the disease may recur in the allograft. The pathogenesis of amyloidosis Hilton 10-20, 200 First Street, SW, Rochester derived from leukocyte cell–derived chemotaxin 2 amyloidosis has not yet been elucidated. It could be a result of MN 55905. Email: nasr. leukocyte cell–derived chemotaxin 2 overexpression by hepatocytes either constitutively (controlled by yet- [email protected] uncharacterized genetic defects) or secondary to hepatocellular damage. It is critical not to misdiagnose amy- loidosis derived from leukocyte cell–derived chemotaxin 2 amyloidosis as Ig light chain–derived amyloidosis to avoid harmful chemotherapy. Clin J Am Soc Nephrol 10: 2084–2093, 2015. doi: 10.2215/CJN.12551214

Introduction chemotaxin 2 (ALECT2) in a patient with nephrotic Amyloidosis is an uncommon group of diseases char- syndrome and renal insufficiency who underwent ne- acterized by extracellular deposition of insoluble fibrils, phrectomy for resection of renal cell carcinoma. Three which result from abnormal folding of . Amy- recent large studies (5,11,12) that included a total of loid deposits characteristically stain with Congo red 144 patients (112 patients with renal amyloidosis and and show anomalous color change (so-called apple- 32 patients with liver amyloidosis) have established green birefringence) when examined under polarized that ALECT2 amyloidosis is now a frequent type of light. Thirty-one precursor proteins of have renal and hepatic amyloidosis and highlighted its dis- been identified so far (1). Amyloidosis can be systemic tinct clinical and pathologic characteristics, including or localized. In the United States and Europe, Ig light clear ethnic predisposition, typical presentation with chain–derived (AL) amyloidosis is, by far, the most chronic renal insufficiency with or without proteinuria, frequent type, whereas in developing countries, AA and superior patient survival to AL amyloidosis and amyloidosis is more common than AL amyloidosis (2). AA amyloidosis. This mini-review highlights the cur- Kidney involvement is present in most patients with rent status of ALECT2 amyloidosis, including inci- AL amyloidosis (3) and AA amyloidosis (4) and may dence, organ distribution, clinical presentation, also occur in several rare hereditary forms of amyloid- pathogenesis, histologic characteristics, renal and pa- osis, such as those derived from fibrinogen A, transthyretin tient survival, poor prognostic indicators, and recur- (ATTR), gelsolin (particularly in homozygotes), lysozyme, rence in the renal allograft. apo AI (AApo AI), AApo AII, and AApo AIV (5–8). The overall renal biopsy incidence of amyloidosis ranges from 1.3% to 4% (5–7,9). Incidence and Ethnic Predisposition In 2008, Benson et al. (10) discovered a new form of ALECT2 amyloidosis is now as common as AA amyloidosis derived from leukocyte cell–derived amyloidosis in the United States. Of 4139 patients with

2084 Copyright © 2015 by the American Society of Nephrology www.cjasn.org Vol 10 November, 2015 Clin J Am Soc Nephrol 10: 2084–2093, November, 2015 Leukocyte Cell–Derived Chemotaxin 2–Associated Amyloidosis, Nasr et al. 2085

clinical amyloidosis diagnosed by (regardless of far, although there was one reported patient with hepatic and the specimen site) at the Mayo Clinic, the four most common cardiac amyloidosis in whom the hepatic (but not cardiac) types were AL (61.7%), ATTR (24.5%), AA (3.7%), and amyloid was proven to be ALECT2 by immunohistochemis- ALECT2 (3.6%) (13). It accounts for 2.7%–10% of patients try (IHC) and sequencing (22). Patients with renal with renal amyloidosis in the United States (5,6,14). In a re- ALECT2 amyloidosis may have amyloid deposits in the bone cent series of 474 patients with biopsy-proven renal amy- marrow (12). Autopsy-based studies are underway in the loidosis from the Mayo Clinic, 86% were Ig derived, 7% southwest United States to confirm the systemic nature of were AA derived, 3% were ALECT2 derived, and 1% ALECT2 amyloidosis and shed some light on its prevalence were fibrinogen A derived (6). In another United States se- and pathogenesis. ries from Nephropath of 414 patients, 83% were Ig derived, 10% were ALECT2 derived, and 5% were AA derived (5). In this series, ALECT2 amyloidosis accounted for 54% of pa- Clinical Characteristics Table 1 summarizes the clinical findings from the three tients with renal amyloidosis (2% of total kidney biopsies largest series of ALECT2 amyloidosis reported to date. Sim- received during the study period) from the southwestern ilar to AL amyloidosis, ALECT2 amyloidosis mainly affects United States (New Mexico, Arizona, and far west Texas) the older population. Patients with kidney involvement are (5), which has a high concentration of Hispanics. ALECT2 slightly older at diagnosis (median age of 69 years old) than amyloidosis is also a frequent cause of hepatic amyloid- those with liver involvement (median age of 61 years old) osis (11,15). In a recent series of 130 patients with liver (5,11,12). There have been only five reported patients who amyloidosis diagnosed by proteomics at the Mayo Clinic, were younger than 50 years old at diagnosis, the youngest of 62% were AL, 25% were ALECT2, 7% were AApo AI, 4% whom was 33 years old with hepatic ALECT2 amyloidosis were AA, 2% were ATTR, and 1% amyloidosis derived from (11,12). Most patients with renal ALECT2 amyloidosis pres- lysozyme (11). ent with chronic renal insufficiency (5,12,16). The mean se- In sharp contrast to other types of systemic amyloidosis, rum at diagnosis was 3 mg/dl in the series by ALECT2 amyloidosis exhibits a strong ethnic bias, with Said et al. (12) and 2.8 mg/dl in the series by Larsen et al. (5) 88%–92% of reported patients being Hispanics (5,11,12). (Table 1). In contrast to other forms of renal amyloidosis, All reported Hispanic patients who disclosed their origin proteinuria is an inconsistent finding in renal ALECT2 amy- were of Mexican descent (12,16). Because Mexican Amer- loidosis and lacking altogether in 21%–67% of patients (5,12). icans constitute the largest group of United States Hispan- Full nephrotic syndrome is uncommon in renal ALECT2 amy- ics (63%), it is still unknown if they are more likely to loidosis, which was present in only 10% of patients in the series develop ALECT2 than Unites States Hispanics originating by Said et al. (12) Rarely, renal ALECT2 amyloidosis is an in- from other countries. Additional ethnic groups described cidental pathologic finding found in the non-neoplastic paren- to develop ALECT2 with an increased frequency included chyma of nephrectomy specimens performed for resection of Punjabis, First Nations people in British Columbia, Arabs, renal cell carcinoma, which was the case in four (6%) patients in Israelis, and Native Americans (5,12,17,18). It is worth not- the series by Said et al. (12). Microhematuria is uncommon, ing that Native-American ancestry is shared by both First encountered in 16% of patients in one study (12). Chronic hy- Nations people and Hispanics (higher level in Mexicans pertension and mellitus are frequent (Table 1) (5,12). A and Ecuadorians compared with Colombians, Puerto Ricans, minority of reported patients with renal ALECT2 had carci- and Dominicans) (19), which may explain the bias toward noma (10,12,21), which was present in 13% of patients in one both of the these populations (17). As discussed later, the study (12). A patient with kidney and lung ALECT2 amyloid- strong cosegregation of ALECT2 amyloidosis with Mexican- osis presenting with acute renal failure and hemoptysis has been American ethnicity together with the reported familial occur- reported (21). This patient had positive myeloperoxidase- rence in two siblings and the frequent G-allele homozygosity ANCA, and therefore, his pulmonary-renal syndrome was raise the possibility that this disease may represent another likely caused by small-vessel vasculitis and not amyloidosis, form of familial amyloidosis (5,12,20). despite the lack of crescents in the limited renal biopsy sample (eight glomeruli only) (21). Hepatic ALECT2 amyloidosis is frequently discovered as Affected Organs an incidental finding in liver biopsy performed during sur- ALECT2 amyloidosis is likely a systemic form of amy- gery for nonhepatic conditions or specimens that show other loidosis with predominant involvement of kidney and pathology that explains the liver dysfunction, such as chronic liver. Of 120 patients with ALECT2 amyloidosis diagnosed viral hepatitis or steatohepatitis (11). The most frequent clinical by liquid chromatography/mass spectrometry (LC/MS) at abnormality, if any, in patients with liver ALECT2 amyloidosis the Mayo Clinic between 2007 and 2012, 72 affected the is an elevation of alkaline phosphatase (11). In contrast, kidney, 36 liver, five spleen, three prostate, and one each most patients with liver AL amyloidosis have evidence of from gallbladder, pancreas, small bowel, and parathyroid liver abnormality, most commonly hepatomegaly and ele- gland (12). Interestingly, most patients with ALECT2 amy- vated liver function tests (11). Rarely, ALECT2 amyloidosis loidosis reported so far were diagnosed by kidney biopsy can cause portal hypertension and variceal bleeding (23). in patients without clinically evident extrarenal organ in- volvement (5,12,17) or liver biopsy in patients without clin- ically evident extrahepatic organ involvement (11). A Pathogenesis patient with biopsy-proven pulmonary ALECT2 amyloid- Leukocyte cell–derived chemotaxin 2 (LECT2) is a 16-kD osis was also reported (21). No patient with cardiac cytokine first isolated by Yamagoe et al. (24) in 1996. It is ALECT2 amyloidosis has been confirmed histologically so widely conserved in vertebrates and identical to bovine 2086 Clinical Journal of the American Society of Nephrology

Table 1. Clinical characteristics of leukocyte cell–derived chemotaxin 2 amyloidosis

Said et al. (12; Larsen et al. (5; Mereuta et al. (11; Series Renal ALECT2) Renal ALECT2) Liver ALECT2)

No. of patients 72 40 32 Organs with histologically proven Kidney in all, liver in one, Kidney in all, liver Liver in all involvement duodenum in one, in one, and and adrenal in one prostate in one Median age (range), yr 65.5 (43–88) 70.5 (52–86) 60.5 (33–79) ,50, % 3 0 9 Men/women 37/35 25/15 12/20 Hispanic ethnicity, % 92 88 88 Mean serum creatinine (range) at 32.8NA diagnosis, mg/dl Proteinuria, % 79 33 NA Nephrotic-range proteinuria, % 33 23 NA Median 24-h urine , g/d 1 0.6 NA Other pathology, % 26 32 66 Diabetes mellitus, % 26 38 NA Hypertension, % 68 50 NA Monoclonal gammopathy, % 10 8 NA Family history of amyloidosis, % 0 5 NA Mean duration of follow-up, mo 31 50 NA Progression to ESRD 25/64 (39%) 6/21 (29%) NA

ALECT2, amyloidosis derived from leukocyte cell–derived chemotaxin 2; NA, not applicable. chondromodulin-II, a cartilage-derived protein involved in at the N terminus. A polymorphism in the LECT2 gene has bone repair. The secreted protein consists of 133 amino acids been identified in which there is a DNA codon change from and has three intermolecular disulfide bonds (25). The ter- ATC (A allele) to GTC (G allele) at position 172 (SNP rs31517), tiary structure of this protein is still unknown. Its gene in resulting in replacement of by at position humans is located on 5q31.1-q32 (26). The 40 of mature protein (26). The G allele is common, with an LECT2 gene also encodes an 18-amino acid secretory signal overall frequency of 0.477; 51% of healthy Mexicans (27)

Figure 1. | Proposed pathogenesis of amyloidosis derived from leukocyte cell–derived chemotaxin 2 (ALECT2) amyloidosis. The patho- genesis of ALECT2 amyloidosis is still unknown. It is likely caused by leukocyte cell–derived chemotaxin 2 (LECT2) overexpression by hep- atocytes either constitutively resulting from a combination of the common G/G genotype and yet to be defined genetic mutations or compensatory to hepatocellular damage. Upregulation of LECT2 overexpression by hepatocytes potentially leads to production of misfolded LECT2 protein. The presence of unstable LECT2 protein combined with several other factors, such as increased local concentrations, inter- actions with components of extracellular matrix, such as laminin and type IV collagen, and bindings with serum amyloid P (SAP), apoE, and glycosaminoglycans (GAGs), particularly heparin sulfate, ultimately lead to amyloid fibril formation and stabilization. The accumulations of large amounts of ALECT2 amyloid fibrils in the interstitium can disrupt kidney or liver architecture and impede their physiologic functions. Clin J Am Soc Nephrol 10: 2084–2093, November, 2015 Leukocyte Cell–Derived Chemotaxin 2–Associated Amyloidosis, Nasr et al. 2087

Figure 2. | Renal pathology in amyloidosis derived from leukocyte cell–derived chemotaxin 2 (ALECT2) amyloidosis. (A) The case depicted shows extensive interstitial, glomerular, and vascular congophilic amyloid deposition. This patient had subnephrotic proteinuria (2.5 g/d) at diagnosis. Magnification, 340. (B) Same field as in A. The congophilic amyloid deposits show anomalous colors (red, yellow, and green) under polarized light. Magnification, 340. (C) The case depicted is from a patient who had a serum creatinine of 2.3 mg/dl at biopsy without pro- teinuria. There is diffuse cortical interstitial and focal arteriolar amyloid deposition with sparing of glomeruli (Congo red stain). Magnification, 3100. (D) This patient exhibits extensive involvement of cortical interstitium and glomeruli. The medullary interstitium (arrow) is spared (Congo red stain). Magnification, 320. (E) A low-power electron microscopic image showing several interstitial collections of amyloid deposits (arrows). Magnification, 35800. (F) A higher-magnification image reveals the fibrillar substructure of deposits. Magnification, 349,000. and 47% of healthy Japanese individuals (28) are homozy- unpublished data). LECT2 expression is upregulated by ac- gous of the G allele. A Japanese study found that the A/A tivation of the Wnt/b-catinin signaling pathway in the genotype is associated with higher severity of rheumatoid liver, a commonly dysregulated pathway in carcinogenesis arthritis (28). (29). LECT2 receptor(s) and its downstream signaling path- LECT2 is synthesized mainly by hepatocytes. IHC studies ways are yet to be characterized. A study on Ayu (pleco- showed that LECT2 expression is restricted to pericentral glossus altivelis) showed that LECT2 interacts with a vein hepatocytes in normal mouse liver, whereas it is diffuse C-type lectin receptor (32). Chen et al. (33) recently showed throughout the lobule hepatocytes in normal human liver that the inhibitory function of LECT2 on hepatocellular car- (29,30). One study found that LECT2 protein is also ex- cinoma is mediated by binding and inactivation of MET pressed in a variety of other cells in many organs, including receptor, leading to blockage of vascular invasion and me- adipocytes, smooth muscle cells, endothelial cells, and ep- tastasis of . Other studies showed ithelial cells, although of much weaker and more variable that LECT2 negatively regulates the homeostasis of NKT expression than in hepatocytes (31). We, however, have not cells in the liver (34,35). found any convincing positive intracellular LECT2 staining The turnover rate of LECT2 is unknown. Its half-life was by IHC or in situ hybridization outside the liver (A. Dogan, predicted to be short because of the low molecular weight 2088 Clinical Journal of the American Society of Nephrology

Figure 3. | Liver pathology in amyloidosis derived from leukocyte cell–derived chemotaxin 2 (ALECT2) amyloidosis. (A) There are periportal deposits of strongly congophilic amyloid deposits. Magnification, 3100. (B) In this low-power image, strongly congophilic amyloid deposits are seen surrounding the central veins. In contrast to Ig light chain–derived amyloidosis, the perisinusoidal spaces are spared. Magnification, 340. (C) On high magnification, ALECT2 deposits form large acellular globules, which appear blue on trichrome stain. Magnification, 3200.

(36). Plasma LECT2 concentration in normal individuals is amyloidosis were found to be normal (16). DNA sequenc- 19.763.4 ng/ml (37). Its serum level is increased in liver ing performed in 26 patients with ALECT2 amyloidosis diseases, such as acute liver injury (38), hepatocellular carci- did not detect any mutation in the LECT2 gene (5,10,11,16). noma (39), fatty liver (40), obesity (40), and Interestingly, all patients tested were homozygous for the (36). In contrast, a recent study showed that plasma LECT2 G allele (5,10,11,16). It is possible that the change from iso- concentrations in patients with sepsis were remarkably low leucine to valine in the LECT2 protein decreases its stability and negatively correlated with the disease severity (37). and allows it to undergo amyloidogenic conformational al- LECT2 protein was initially purified from a culture fluid terations (Figure 1). Recent data indicated that LECT2 is ca- of phytohemagglutinin-activated human T cell leukemia pable of self-oligomerization in vitro (48). Oligomerization SKW-3 cells as a potential chemotactic factor for human could be an intermediate step toward fibril formation, (24). Subsequent studies indicated that it is a which has been shown recently in b2-microglobulin amy- multifactorial cytokine involved in , cell prolif- loidosis (49). Because of its strong ethnic bias and the re- eration, immunomodulation, damage/repair process, tu- ported familiar occurrence in two brothers, ALECT2 mor suppression, and glucose metabolism (33,36,41–44). amyloidosis may represent a digenic or polygenic disorder The pathogenesis of ALECT2 amyloidosis is still un- that results from a combination of the common G/G geno- known. LECT2 is a folded protein with a b-sheet structure type and other genetic mutations that have yet to be char- (45,46). The entire LECT2 protein was found in ALECT2 acterized (Figure 1) (5,20). Additional studies are needed to fibrils (10,27,47). It is unlikely that proteolytic degradation determine if ALECT2 is, in fact, a genetic disorder. It is also is necessary for fibril formation in ALECT2 amyloidosis possible that ALECT2 amyloidosis is caused by interfer- in opposition to most other amyloid precursor proteins. ence, possibly due to a genetic defect, in the catabolic or Mereuta et al. (11) showed that hepatocytes in patients transport pathways of LECT2, resulting in an increased with liver ALECT2 amyloidosis strongly and uniformly local tissue concentration and amyloid fibril formation expressed LECT2 mRNA, whereas hepatocytes of normal (12,16,47). Another possible etiology is an alteration in a individuals and patients with AL amyloidosis did not, binding partner of the LECT2 protein in the serum result- suggesting that constitutive or compensatory LECT2 over- ing in increased levels of free circulating LECT2. Tubular expression could be responsible for ALECT2 amyloidosis and glomerular cells in patients with renal ALECT2 amy- (Figure 1). Because LECT2 is involved in hepatocarcino- loidosis do not overexpress LECT2 mRNA (S.H. Nasr, un- genesis and severe liver injury, it is possible that hepato- published data). This finding and the documented disease cellular damage causes upregulation of LECT2 expression recurrence in the renal allograft argue against the possibil- and consequently, ALECT2 amyloidosis (11). However, ity that renal ALECT2 amyloidosis is caused by locally pro- LECT2 plasma levels tested in a few patients with ALECT2 duced LECT2. Currently, we do not know whether Clin J Am Soc Nephrol 10: 2084–2093, November, 2015 Leukocyte Cell–Derived Chemotaxin 2–Associated Amyloidosis, Nasr et al. 2089

Figure 4. | Laser microdissection/mass spectrometry in a patient with renal amyloidosis derived from leukocyte cell–derived chemotaxin 2 (ALECT2) amyloidosis. (A) Glomerular and (B) interstitial congophilic amyloid deposits visualized under fluorescent light and marked for microdissection. Magnification, 3200. (C) Vacant spaces after microdissection of glomerular amyloid deposits. Magnification, 3200. (D) List of amyloid-associated proteins identified within the deposits by liquid chromatography/mass spectrometry (LC/MS) from a patient with ALECT2 displayed by Scaffold (proteome software). The four columns represent separate microdissected samples run in replicate. The spectra value indicates the total number of mass spectra collected on the mass spectrometer and matched to the protein using the proteomic software. A higher number of mass spectra is indicative of greater abundance of protein and greater amino acid sequence coverage. Our clinical amyloid testing requires a minimum number of four spectra with .95% probability in all samples before the protein identification will be deemed clinically valid. In this case, the presence of abundant spectra for apoE and serum amyloid P is indicative of amyloid, whereas the presence of abundant spectra for leukocyte cell–derived chemotaxin 2 (LECT2) establishes the type as ALECT2 amyloidosis.

ALECT2 deposition is a slow process that begins early in Congo red (5) and show anomalous colors, so called apple- life and remains undetected until significant accumulation green birefringence, under polarized light (Figure 2B). has occurred or whether it is a more rapid process that Similar to other forms of renal amyloidosis, the fibrils ul- begins later in life (5). trastructurally appear randomly oriented with a mean di- ameter of 7–12 nm (Figure 2, E and F). Glomerular amyloid spicules, which result from parallel arrangement Pathologic Characteristics of amyloid fibrils perpendicular to the glomerular base- Histologically, renal ALECT2 amyloidosis shows pref- ment membranes, are far less common than in AL amyloid- erential interstitial involvement, which is usually diffuse osis (6). Immunofluorescence is usually negative, although (Figure 2, A–D) (5,6,12,14,16). The glomerular and vascu- false-positive staining for IgG with/without staining for lar amyloid deposits are variable, ranging from absent IgM, IgA, k,andl may rarely occur (12), albeit with a lesser (Figure 2C) to mild to marked (Figure 2, A and B) (5,12). frequency than in AA deposits (6). A minority (9%) of pa- This is different from AL amyloidosis and AA amyloid- tients with ALECT2 amyloidosis show false-positive stain- osis, in which glomeruli and vessels are the prime sites of ing for serum amyloid A (SAA) (12). Importantly, concurrent amyloid deposition (6). Contrary to AApo AI amyloidosis renal disease was present in 32% and 26% of patients in the and AApo AIV amyloidosis, which mainly affect the med- studies by Larsen et al. (5) and Said et al. (12), respectively, ullary interstitium, ALECT2 amyloidosis shows a predom- with diabetic nephropathy being the most common lesion inant involvement of cortical interstitium (Figure 2D) followed by IgA nephropathy and membranous nephropa- (5,12). ALECT2 deposits stain strongly positive with thy (5,12). Compared with patients with ALECT2 amyloidosis 2090 Clinical Journal of the American Society of Nephrology

without concurrent renal disease on biopsy, those with con- distinctive globular appearance (Figure 3) (11). As mentioned current renal disease have higher proteinuria and lower renal above, most specimens with liver ALECT2 deposits show amyloid load (consistent with ALECT2 amyloidosis detection other pathology that may account for liver dysfunction, at an earlier stage) (12). most commonly chronic hepatitis C and steatohepatitis (11). As in the kidney, ALECT2 deposits in the liver have a char- acteristic histologic morphology. In contrast to AL deposits, which typically exhibit a perisinusoidal distribution pattern, Diagnosis ALECT2 deposits are seen preferentially surrounding the cen- Typing amyloid deposits by LC/MS-based proteomics is tral veins and in the periphery of portal tracts and exhibit a currently the best tool to diagnose ALECT2 amyloidosis and other forms of amyloidosis because of its high sen- sitivity and specificity and because it is a single test that can detect the culprit protein in contrast to IHC typing of amy- loidosis, which requires staining for multiple antibodies us- ing several tissue sections (6,50,51). LECT2 protein has many lysine and arginine residues and therefore, can readily be digested by trypsin into peptides, and the amino acid se- quence of the peptides can be determined by LC/MS. The diagnosis of ALECT2 amyloidosis by LC/MS is made ac- cording to clinically established criteria by identification of LECT2 peptide spectra and amyloid-associated proteins (serum amyloid P [SAP] and apoE) (Figure 4) (11,51). Be- cause plasma concentration of LECT2 is trivial, contamina- tion of amyloid deposits by serum LECT2 is not an issue, and the diagnosis is usually straightforward. Unfortu- nately, clinical amyloid typing by proteomics is available only in few selected centers, such as the Mayo Clinic. There Figure 5. | Immunohistochemical staining for leukocyte cell–derived are now several commercially available antibodies for IHC chemotaxin 2 (LECT2). Glomerular and interstitial amyloid deposits are detection of LECT2 that seem to be highly sensitive (Figure strongly positive for LECT2 by immunohistochemistry in this patient 5); however, weak false-positive staining may occur (52), with renal amyloidosis derived from LECT2 amyloidosis. Magnifi- which may result from aggressive antigen retrieval (53). cation, 3100. Therefore, it is crucial that LECT2 antibody is carefully

Figure 6. | Proposed algorithm for diagnosis of amyloidosis derived from leukocyte cell–derived chemotaxin 2 (ALECT2) amyloidosis. AL, Ig light chain–derived; IHC, immunohistochemistry; LECT2, leukocyte cell–derived chemotaxin 2; SAA, serum amyloid A. Clin J Am Soc Nephrol 10: 2084–2093, November, 2015 Leukocyte Cell–Derived Chemotaxin 2–Associated Amyloidosis, Nasr et al. 2091

validated and optimized for the diagnosis of ALECT2 (53). visceral AA deposits in mice (57). It is critical not to mis- In cases that exhibit only weak staining for LECT2, false- diagnose ALECT2 amyloidosis as AL amyloidosis to avoid positive staining for SAA, or staining for Ig light or heavy harmful therapy (20). This error may occur, because chains by immunofluorescence or immunoperoxidase, con- ALECT2 amyloidosis has only recently been recognized, firmation by LC/MS is strongly recommended. When am- most patients are elderly, and a minority have monoclonal yloid typing is performed by IHC, it is critical that the gammopathy (comparable with the general elderly popu- testing is done with a panel of antibodies against several lation) (5,12). In one series, four (6%) patients received che- types of amyloidosis, so-called comparative IHC, instead motherapy with or without stem-cell transplant for an of staining for a single precursor protein (54). In general, erroneous diagnosis of AL amyloidosis (12). better results are obtained if amyloid typing by IHC is per- formed in specialized laboratories (54–56). Of note, mono- clonal gammopathy of undetermined significance was Summary present in 10% and 8% of patients reported by Said et al. Nephrologists and pathologists should maintain a high (12) and Larsen et al. (5), respectively, highlighting the im- level of suspicion for ALECT2 amyloidosis in older indi- portance of accurate typing of amyloid deposits to avoid viduals of Mexican origin who present with renal impair- misdiagnosing ALECT2 amyloidosis as AL amyloidosis ment and bland urinary sediment, regardless of the degree (see below). We propose the algorithm shown in Figure 6 of proteinuria, and a Congo red stain should be performed. for diagnosis of ALECT2 amyloidosis. Hepatic ALECT2 amyloidosis may not be the cause of clin- ically significant liver disease. Recent studies on ALECT2 amyloidosis remind us of the importance of accurate typing of the amyloid deposits and confirmation by LC/MS when Prognosis and Treatment indicated to establish that the culprit proteins causing amy- Patient survival in ALECT2 amyloidosis is significantly loidosis really are Ig light chains and not other proteins, such better than that of AL amyloidosis and AA amyloidosis, as LECT2, TTR, or SAA, to avoid unnecessary and harmful likely because of the rarity or absence of cardiac involve- chemotherapy. ment in ALECT2 amyloidosis. In a series of 72 patients with renal ALECT2 amyloidosis, only 6% of 64 patients with available data died after a median follow-up of 22 months Disclosures (12). The renal survival, however, is guarded; 39% of pa- None. tients in the above-mentioned study progressed to ESRD (12).InthestudybyLarsenet al. (5), in which 32% of patients had concurrent renal disease, follow-up was References available in 21 patients, and two of them had ESRD at 1. Sipe JD, Benson MD, Buxbaum JN, Ikeda S, Merlini G, Saraiva MJ, Westermark P: Nomenclature 2014: Amyloid fibril proteins diagnosis. The remaining 19 patients had an average de- and clinical classification of the amyloidosis. Amyloid 21: 2 terioration in renal function of 0.5 ml/min per 1.73 m per 221–224, 2014 month after a mean follow-up of 50 months (5). Outcome 2. Chugh KS, Datta BN, Singhal PC, Jain SK, Sakhuja V, Dash SC: analysis was performed in the study by Said et al. (12). Pattern of renal amyloidosis in Indian patients. Postgrad Med J 57: Independent predictors of renal survival in renal ALECT2 31–35, 1981 3. Gertz MA, Leung N, Lacy MQ, Dispenzieri A, Zeldenrust SR, amyloidosis without concurrent kidney disease on biopsy Hayman SR, Buadi FK, Dingli D, Greipp PR, Kumar SK, Lust JA, were serum creatinine at diagnosis, with a value of 2.0 Rajkumar SV, Russell SJ, Witzig TE: Clinical outcome of immu- mg/dl being the best cutoff for predicting ESRD, degree noglobulin light chain amyloidosis affecting the kidney. Nephrol of glomerulosclerosis, and presence of diabetes (12). Renal Dial Transplant 24: 3132–3137, 2009 4. Lachmann HJ, Goodman HJ, Gilbertson JA, Gallimore JR, Sabin amyloid load and degree of proteinuria did not predict CA, Gillmore JD, Hawkins PN: Natural history and outcome in outcome (12). systemic AA amyloidosis. N Engl J Med 356: 2361–2371, 2007 There is currently no specific therapy for ALECT2 amy- 5. Larsen CP, Kossmann RJ, Beggs ML, Solomon A, Walker PD: loidosis. 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