—  SPECIALTY CONFERENCE  —

Nephropathology

Case 4 - Lipoprotein Glomerulopathy (LPG)

M. Barry Stokes
New York University Medical Center
New York, New York


Click on each slide thumbnail image for an enlarged view
Clinical History:
A 28-year old American-born Chinese man presented with bilateral ankle edema, foamy urine, sore throat, and new-onset of hypertension (blood pressure 164/114 mm Hg). Urinalysis showed 16 to 20 RBCs/HPF and 24 hour urine collection protein contained 3.9 g protein. Laboratory investigations revealed blood urea nitrogen 34 mg/dL, serum creatinine 2.6 mg/dL, serum albumin 2.5 g/dL, total serum protein 5.0 g/dL, cholesterol 499 mg/dL, triglycerides 485 mg /dL, low-density lipoprotein (LDL) 275 mg/dL and glucose 112 mg/dL. Urine electrophoresis revealed predominantly albumin. Serologic tests for antinuclear antigen, cryoglobulin, paraproteins, and hepatitis B surface antigen were all negative. Anti-streptolysin-O titer, serum C3 and serum C4 levels were within normal limits. Renal ultrasound revealed normal sized kidneys with diffusely increased echogenicity of the renal parenchyma. The patient had no significant past medical history and neither his parents nor his two sisters had a known history of renal disease. A renal biopsy was performed.


Case 4 - Figure 1 - Glomerular capillary lumens are markedly dilated and contain pale-staining, weakly eosinophilic thrombus-like material. This material has a finely lamellar pattern. There is marked thickening of the peripheral capillary wall, with duplication of glomerular basement membranes and focal cellular interposition (Jones methenamine silver stain, 40x).
Case 4 - Figure 2 - Numerous fat droplets (red) in capillary lumens, capillary walls, and Bowman\'s capsule cells and in some tubular epithelial cells (Oil Red O stain of cryosections; 40x).


Case 4 - Figure 3 - Electron micrograph: large aggregates of finely vacuolated osmiophilic material with a concentric lamellated appearance in a capillary lumen.
Case 4 - Figure 4 - Electron micrograph: similar finely vacuolated osmiophilic material in the subendothelial region of a capillary wall and in the adjacent Bowman\'s capsule.

Material for review: 2 kodachromes displaying light microscopic findings (Jones' methenamine silver, 40x), Oil Red O stain (of cryosections, 40x), and 2 EM prints.

Renal Biopsy Findings
By light microscopy, forty-four glomeruli were examined, four of which were globally sclerotic and fourteen of which showed segmental sclerosis with obliteration of capillary lumens, swelling of overlying visceral epithelial cells and adhesions to Bowman's capsule. The non-sclerotic glomeruli were diffusely enlarged with moderate to severe mesangial hypercellularity and matrix increase and focal mesangiolysis. Capillary lumens showed widespread aneurysmal dilatation containing pale eosinophilic foamy material that did not stain with PAS or Trichrome (kodachrome 1) and had a vaguely laminated appearance under high power magnification. Peripheral capillary walls were diffusely thickened with frequent duplication of glomerular basement membrane and focal cellular interposition. No basement membrane "spikes" were seen. Some capillary lumens contained entrapped red blood cells subjacent to the capillary wall. Podocytes focally contained large cytoplasmic protein droplets. Two glomeruli showed possible fibrocellular crescents but without features of underlying tuft necrosis or disruption of Bowman's capsule basement membrane. Occasional foam cells were identified in areas of sclerosis. Approximately 20% of the cortex showed interstitial fibrosis and tubular atrophy accompanied by a patchy interstitial mononuclear inflammatory cell infiltrate. No interstitial foam cells were seen. Some proximal tubular cells contained small cytoplasmic protein and lipid droplets but most were histologically unremarkable. Small arteries and arterioles showed moderate medial thickening and hyalinosis but no vacuolization or other degenerative changes. No intravascular thrombi were seen. One arteriole showed intraluminal aggregates of acellular granular material, similar to that seen in the glomerular capillaries. Peritubular capillaries were unremarkable.

Immunofluorescence microscopy showed trace irregular staining for IgG, C3, and both light chains in periphery capillary walls. Oil red O stain demonstrated numerous fat droplets in capillary lumens, capillary walls, parietal epithelial cells and in some tubular epithelial cells (kodachrome 2). The lipid material stained diffusely and strongly for apo E and apo B.

Electron microscopy disclosed large aggregates of finely vacuolated and granular osmiophilic material, focally with a concentric lamellated appearance, in capillary lumens, in the subendothelial space and in some mesangial areas. Glomerular basement membranes showed focal splitting and cellular interposition. Endothelial cells were swollen and podocyte foot processes were widely effaced (> 80%). No immune type electron densities, endothelial cell tubuloreticular inclusions, or other cytoplasmic inclusions were seen.

Pathologic diagnosis: Lipoprotein glomerulopathy (LPG)

Differential diagnosis
This includes hereditary forms of LPG linked to apo E variants. See below.

Follow-up
Treatment with corticosteroids was stopped after two weeks when an episode of pneumonia led to septic shock. Treatment with levastatin for three years followed by cholestyramine for four months led to a gradual decrease in the serum triglyceride and total cholesterol levels. Over the next eight years, the patient had persistent heavy proteinuria and edema and gradually deteriorating worsening renal function leading to dialysis. He received a cadaveric renal transplant complicated after two years by one episode of mild acute rejection (Banff/CCTT Grade Ia) with similar glomerular findings as in the native kidney. Two years later, the patient continues to have 3+ proteinuria and stable graft function (creatinine 1.5 mg/dL).

Discussion
First mentioned in a review of renal lipidoses by Faraggiana and Churg in 19871  , the term "lipoprotein glomerulopathy" was coined by Saito et al. to describe the novel glomerular findings of lipoprotein thrombi in a 57 year old Japanese woman and her sister who both had proteinuria and a serum lipid profile suggestive of type III hyperlipoproteinemia (elevated plasma levels of apolipoprotein (apo)-E and triglyceride-enriched lipoproteins)2  . Subsequent investigators have shown by immunofluorescence3, 4  and immunoelectron3  microscopy that these lipid aggregates contain apolipoprotein apo E. Approximately thirty-two cases of LPG have been described (reviewed in5  ), mostly among Japanese individuals with only rare cases documented in Caucasian and Chinese populations.3,6,7  There is a 2:1 male preponderance and a wide age distribution (2 weeks–69 years) although most cases present with heavy proteinuria in adult life8  . At least 50% of patients progressed to renal failure 1 to 27 years after onset5  . Familial occurrence2  , recurrence in transplants6  and the association with abnormal levels of apo E-containing lipoproteins suggested a hereditary basis for LPG linked to abnormalities of the apo E gene.

Apo E is a polymorphic 299-amino acid glycoprotein that mediates hepatic clearance of triglyceride-rich lipoproteins from the circulation via binding to the LDL receptor (LDL-R) and to the chylomicron remnant receptor. Apo E has three major genetically determined isoforms, E2, E3 and E4, encoded for by three alleles ( e2,e3 and e4) at a single gene locus on chromosome 19. e3 is the wild type allele, occurring in 50-90% of the different populations worldwide. Apo E2 displays defective LDL-R binding (approximately 2% that of apo E3 or apo E4) and homozygous E2/2 is associated with familial type III hyperlipoproteinemia. All of the initial LPG patients studied were found to have apo E2 (usually with a heterozygous E2/E3 or E2/4 phenotype), even though the allele frequency of apo E is less than 15% in the Japanese population. Sequencing of the apo E gene in these patients led to the discovery of several novel isoforms in LPG: two missense mutations, (Arg145 ®Pro (apo E Sendai)9  and Arg25 ®Cys (apo E Kyoto))10  and two in-frame deletions, (residues 141-143 (apo E Tokyo/Maebashi)11  and residues 156-173 (apo E1))12  . Apo E2-Sendai, the commonest variant, was found in 11 of 14 Japanese patients tested, including three families with an autosomal recessive pattern of inheritance.5  The preponderance of LPG in the relatively static and homogenous Japanese population suggests a founder effect due to shared common ancestor(s) possessing these novel apo E isoform(s).

The pathologic findings in LPG are highly distinctive and the differential diagnosis is essentially limited to the different apo E variants that have been linked to this condition. In particular, electron microscopy reveals characteristic lamellar accumulations of variable sized lipid droplets having a granular or vacuolar appearance. In milder cases, lipid deposits may localize to the mesangium first and then extend into the subendothelial space. Other renal lipidoses that may superficially resemble LPG at the light microscopic level include lecithin-cholesterol acyl transferase (LCAT)-deficiency, Fabry disease, Niemann-Pick disease, Gaucher disease, mucolipidosis type II (I-cell disease), and familial type III dysbetalipoproteinemia1  . With the exception of LCAT-deficiency and Fabry disease, clinical renal involvement in these conditions is rare, and each of these conditions has other clinical and ultrastructural characteristics that permit distinction from LPG. LCAT-deficiency is associated with "bubbly" thickening of the glomerular basement membrane in a membranous pattern, mesangial sclerosis, and foamy macrophage accumulation in capillaries and mesangium. EM shows small solid, thread-like, or lamellar dense structures in otherwise empty-appearing lacunae. Fabry disease is characterized by vacuolated podocytes and distal tubular epithelial cells and EM findings of whorled lamellar scroll-like inclusions, so-called "zebra bodies" or myelin bodies, in these cells and in vascular endothelium. Gaucher disease rarely involves the kidney following splenectomy, with characteristic "wrinkled paper" cells seen in glomerular capillaries and mesangium. These cells stain strongly PAS-positive in frozen sections and EM shows needle-shaped inclusions. Rare apo E2 homozygous individuals with familial type III dysbetalipoproteinemia have developed a type of "glomerular atherosclerosis" characterized by glomerulosclerosis with prominent foamy macrophage infiltrates in mesangium and capillary walls13  . This lesion is morphologically distinguishable from LPG at the light microscopic level. Of note, LPG may coexist with other glomerular diseases, including membranous nephropathy, IgA nephropathy and lupus nephritis14  .

The pathogenesis of the lipoprotein "thrombi" in LPG is unknown. Recently, Ishigaki et al. described the rapid development of LPG in apo E-deficient mice following transfection with apo E-Sendai, suggesting a direct pathogenic role for apo E-Sendai.15  However, the specificity of these findings has been challenged by another study that showed LPG-like lesions may develop spontaneously in ageing hyperlipidemic apo-E deficient mice in the absence of apo E Sendai.16  LPG has also been described in two siblings with non-mutated apo E217  and not all family members carrying apo E mutations develop LPG, implying that other genetic and environmental factors, in addition to variant apo E isoform, are necessary for disease expression. A direct role for hyperlipidemia is excluded by the occurrence, albeit rarely, of LPG in normolipidemic individuals18  and by the absence of LPG in patients with type III dysbetalipoproteinemia, who have the same hyperlipidemic profile. Although the recurrence of LPG following transplantation excludes a primary glomerular abnormality in this condition, the unique localization of lipoprotein "thrombi" to glomeruli suggests that intraglomerular lipid trafficking probably plays a central pathogenetic role. Structural alterations in apo E variants might promote self-aggregation of lipoproteins in the highly concentrated microenvironment of the glomerular capillary where increased endothelial binding by aberrant apo E might promote lipoprotein accumulation.19  Binding to mesangial cell apo E receptors probably mediates clearance of lipoproteins from the glomerular capillary and it is possible that defective receptor binding by apo E variants impedes lipoprotein efflux from the mesangial region. Several LPG-associated apo E mutations occur within the LDL-R binding domain (spanning residues 136 to 150) suggesting a possible role for altered LDL-R binding.19  Persistent proteinuria and oxidation of accumulated lipoproteins probably contribute to progressive sclerosis and renal failure via activation and amplification of pro-fibrogenic signaling pathways.20 

Unlike type III familial dysbetalipoproteinemia, systemic manifestations of hyperlipidemia, such as cutaneous xanthomas, corneal arcus and premature atherosclerosis, are very uncommon in LPG. This may reflects the absence of co factors required for these complications, such as obesity, diabetes mellitus, and insulin resistance in the relatively small number of cases reported to date.21, 22  There is no specific treatment for LPG. Steroids, immunosuppressants and anticoagulants, have all proved ineffective in preventing progression to renal failure in most cases.5  Lipid-lowering drugs (including fibrates and HMG Co-enzyme A reductase inhibitors) and lipid apheresis may ameliorate the hyperlipidemia but have not been shown to prevent disease progression. Only one patient who had coexistent LPG and IgA nephropathy showed improvement of clinical signs and disappearance of lipoprotein thrombi following treatment with probucol.23  LPG recurs in the renal allograft, either with the nephrotic syndrome (as early as five months in one case)6  or as an incidental finding.24  The subject presented here has stable graft function two years following the discovery of recurrent LPG in his allograft kidney.

In conclusion, LPG is a rare genetic disorder of lipid metabolism whose clinical course is dominated by lipoprotein accumulation in glomeruli, often leading to the nephrotic syndrome and progressive renal failure. Some cases are related to heritable novel apo E variants with an autosomal recessive pattern of inheritance. However, LPG is genetically heterogeneous and other factors, both genetic and environmental, most likely contribute to its clinical expression.

References

  1. Faraggiana T, Churg J: Renal lipidoses: a review. Hum Pathol 18:661-679, 1987
  2. Saito T, Sato H, Kudo K, Oikawa S, Shibata T, Hara Y, Yoshinaga K, Sakaguchi H: Lipoprotein glomerulopathy: glomerular lipoprotein thrombi in a patient with hyperlipoproteinemia. Am J Kidney Dis 13:148-153, 1989
  3. Zhang P, Matalon R, Kaplan L, Kumar A, Gallo G: Lipoprotein glomerulopathy: first report in a Chinese male. Am J Kidney Dis 24:942-950, 1994
  4. Watanabe Y, Ozaki I, Yoshida F, Fukatsu A, Itoh Y, Matsuo S, Sakamoto N: A case of nephrotic syndrome with glomerular lipoprotein deposition with capillary ballooning and mesangiolysis. Nephron 51:265-270, 1989
  5. Saito T, Oikawa S, Sato H, Sasaki J: Lipoprotein glomerulopathy: renal lipidosis induced by novel apolipoprotein E variants. Nephron 83:193-201, 1999
  6. Mourad G, Cristol JP, Turc-Baron C, Djamali A: Lipoprotein glomerulopathy: a new apolipoprotein-E-related disease that recurs after renal transplantation. Transplant Proc 29:2376, 1997
  7. Meyrier A, Dairou F, Callard P, Mougenot B: Lipoprotein glomerulopathy: first case in a white European. Nephrol Dial Transplant 10:546-549, 1995
  8. Shimizu M, Ohno T, Kimoto H, Hosono S, Nozawa M: A newborn infant with lipoprotein glomerulopathy associated with congenital nephrotic syndrome. Pediatr Int 43:78-80, 2001
  9. Oikawa S, Matsunaga A, Saito T, Sato H, Seki T, Hoshi K, Hayasaka K, Kotake H, Midorikawa H, Sekikawa A, Hara S, Abe K, Toyota T, Jingami H, Nakamura H, Sasaki J: Apolipoprotein E Sendai (arginine 145-->proline): a new variant associated with lipoprotein glomerulopathy. J Am Soc Nephrol 8:820-823, 1997
  10. Matsunaga A, Sasaki J, Komatsu T, Kanatsu K, Tsuji E, Moriyama K, Koga T, Arakawa K, Oikawa S, Saito T, Kita T, Doi T: A novel apolipoprotein E mutation, E2 (Arg25Cys), in lipoprotein glomerulopathy. Kidney Int 56:421-427, 1999
  11. Konishi K, Saruta T, Kuramochi S, Oikawa S, Saito T, Han H, Matsunaga A, Sasaki J: Association of a novel 3-amino acid deletion mutation of apolipoprotein E (Apo E Tokyo) with lipoprotein glomerulopathy. Nephron 83:214-218, 1999
  12. Ando M, Sasaki J, Hua H, Matsunaga A, Uchida K, Jou K, Oikawa S, Saito T, Nihei H: A novel 18-amino acid deletion in apolipoprotein E associated with lipoprotein glomerulopathy. Kidney Int 56:1317-1323, 1999
  13. Amatruda JM, Margolis S, Hutchins GM: Type 3 hyperlipoproteinemia with mesangial foam cells in renal glomeruli. Arch Pathol 98:51-54, 1974
  14. Saito T, Sato D, Oikawa S: Lipoprotein glomerulopathy: a new aspect of lipid induced glomerular injury. Nephrology 1:17-24, 1995
  15. Ishigaki Y, Oikawa S, Suzuki T, Usui S, Magoori K, Kim DH, Suzuki H, Sasaki J, Sasano H, Okazaki M, Toyota T, Saito T, Yamamoto TT: Virus-mediated transduction of apolipoprotein E (ApoE)-sendai develops lipoprotein glomerulopathy in ApoE-deficient mice. J Biol Chem 275:31269-31273, 2000
  16. Wen M, Segerer S, Dantas M, Brown PA, Hudkins KL, Goodpaster T, Kirk E, LeBoeuf RC, Alpers CE: Renal injury in apolipoprotein E-deficient mice. Lab Invest 82:999-1006, 2002
  17. Sakatsume M, Kadomura M, Sakata I, Imai N, Kondo D, Osawa Y, Shimada H, Ueno M, Miida T, Nishi S, Arakawa M, Gejyo F: Novel glomerular lipoprotein deposits associated with apolipoprotein E2 homozygosity. Kidney Int 59:1911-1918, 2001
  18. Saito T, Sato H, Oikawa S, Kudo K, Kurihara I, Nakayama K, Abe K, Yoshinaga K, Sakaguchi H: Lipoprotein glomerulopathy. Report of a normolipidemic case and review of the literature. Am J Nephrol 13:64-68, 1993
  19. Hoffmann M, Scharnagl H, Panagiotou E, Banghard W, Wieland H, Marz W: Diminished LDL receptor and high heparin binding of apolipoprotein E2 Sendai associated with lipoprotein glomerulopathy. J Am Soc Nephrol 12:524-530, 2001
  20. Ding G, van Goor H, Ricardo SD, Orlowski JM, Diamond JR: Oxidized LDL stimulates the expression of TGF-beta and fibronectin in human glomerular epithelial cells. Kidney Int 51:147-154, 1997
  21. Eto M, Saito M, Nakata H, Iwashima Y, Watanabe K, Ikoda A, Kaku K: Type III hyperlipoproteinema with apolipoprotein E2/2 genotype in Japan. Clin Genet 61:416-422, 2002
  22. de Beer F, Stalenhoef AF, Hoogerbrugge N, Kastelein JJ, Gevers Leuven JA, van Duijn CM, Havekes LM, Smelt AH: Expression of type III hyperlipoproteinemia in apolipoprotein E2 (Arg158 --> Cys) homozygotes is associated with hyperinsulinemia. Arterioscler Thromb Vasc Biol 22:294-299, 2002
  23. Amenomori M, Haneda M, Morikawa J, Nishigaki I, Maeda S, Hidaka H, Kikkawa R, Shigeta Y: A case of lipoprotein glomerulopathy successfully treated with probucol. Nephron 67:109-113, 1994
  24. Miyata T, Sugiyama S, Nangaku M, Suzuki D, Uragami K, Inagi R, Sakai H, Kurokawa K: Apolipoprotein E2/E5 variants in lipoprotein glomerulopathy recurred in transplanted kidney. J Am Soc Nephrol 10:1590-1595, 1999