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Dense Deposit Disease Mimicking a Renal Small VesselVasculitis

Lavleen Singh,* Geetika Singh,* Swati Bhardwaj,† Aditi Sinha,† Arvind Bagga,† and Amit Dinda*

*Department of Pathology and †Division of Pediatric Nephrology, Department of Pediatrics, All India Institute of MedicalSciences, New Delhi, Delhi, India

ABSTRACTDense deposit disease is caused by fluid-phase dysregulation of the alternativecomplement pathway and frequently deviates from the classic membranoprolifer-ative pattern of injury on light microscopy. Other patterns of injury described fordense deposit disease includemesangioproliferative, acute proliferative/exudative,and crescentic GN. Regardless of the histologic pattern, C3 glomerulopathy, whichincludes dense deposit disease and C3 GN, is defined by immunofluorescenceintensity of C3c two or more orders of magnitude greater than any other immunereactant (on a 0–3 scale). Ultrastructural appearances distinguish dense depositdisease and C3 GN. Focal and segmental necrotizing glomerular lesions with cres-cents, mimicking a small vessel vasculitis such as ANCA-associated GN, are a veryrare manifestation of dense deposit disease. We describe our experience with thisunusual histologic presentation and distinct clinical course of dense deposit disease,discuss the pitfalls in diagnosis, examine differential diagnoses, and review the rel-evant literature.

J Am Soc Nephrol 27: ccc–ccc, 2015. doi: 10.1681/ASN.2015020187

Dense deposit disease (DDD) was classi-cally described as a type of membrano-proliferative GN with intramembranouselectron dense deposits on ultrastruc-tural examination.1 The membranoproli-ferative GN pattern is a constellationcomposed of thickened capillary wallswith double contours, glomerular hy-percellularity, and increased mesangialmatrix. Light microscopy (LM) findingsin DDD often deviate from this classicdescription,2 and the entity is nowgrouped under the umbrella term C3glomerulopathy.3

We recently saw a patient with DDDpresenting as a focal and segmental nec-rotizing GN with crescents, reminiscentof a small vessel vasculitis with an unusualclinical course. The diagnostic dilemmaposed by this rare histologic pattern andpitfalls in interpretation of the immuno-fluorescence (IF) are discussed.

CASE REPORT

A 10-year-old boy was admitted withcomplaints of generalized body swellingfor 15 days and hematuria for 10 days. Inaddition, the child had a history of non-pruritic generalized skin rash, right hippain (subsided with analgesics), fever(high-grade, intermittent), and vomitingat the onset. There was no preceding his-tory of pharyngitis, sinusitis, pneumonia,or skin infection. On day 3 of admission,he developed oliguria followed by anuria.The patient was normotensive. His serumcreatinine rose to 7 mg/dl; thus, hemodi-alysis was initiated. Urine microscopyshowed active sediment with full-fielddysmorphic red blood cells. SerumC3was85 mg/dl (normal 70–240) and antinu-clear antibody, ANCA, and viral markers(serologies for HIVand hepatitis B and C)were negative.

The renal biopsy showed a total of 22glomeruli, 10ofwhich showedsegmentalnecrotizing lesions with overlying cellu-lar crescents, fibrin in Bowman’s space,and Bowman’s capsule rupture (Figure 1,A and B). The glomerular capillary lu-mina were suffused by neutrophils; how-ever, no mesangial infiltration was noted.There was no endocapillary/mesangialproliferation, capillary wall thickening,or splitting in any of the glomeruli. Thetubulointerstitium displayed mild inter-stitial edema and focal acute tubular in-jury, along with numerous red blood cellcasts. No vasculitis of arteries or arterio-les or granulomatous inflammation wasnoted. There was no chronicity.

In view of the concomitant skin rash,the differential diagnoses consideredwere ANCA-negative pauci-immunecrescentic GN and Henoch–Schönleinnephritis (HSN). IF revealed focalchunky capillary wall and mesangial de-position of C3 (1+, 0–3+ scale; Figure1C) and fibrin (2+, 0–3+ scale) andwas negative for all Igs. The IF profileexcluded HSN and anti–glomerularbasement membrane (GBM) disease.The focal C3 deposition was initiallyconsidered nonspecific; thus, on the

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Correspondence: Dr. Geetika Singh, Departmentof Pathology, All India Institute of Medical Scien-ces, Teaching Block, First Floor, New Delhi, Delhi,India 110029. Email: ggmed22@gmail.com

Copyright © 2015 by the American Society ofNephrology

J Am Soc Nephrol 27: ccc–ccc, 2015 ISSN : 1046-6673/2701-ccc 1

basis of LM and IF findings, a diagnosisof ANCA-negative pauci-immune cres-centic GN was suggested.

The child was given six pulses of meth-ylprednisolone and 10 days of plasmaexchange. Pulse cyclophosphamide wasstarted at 500 mg/m2 per dose after thecompletion of six methyl prednisolonepulses and was continued at the samedose at 3-weekly intervals for a total offive doses. The urine output improvedand the patient was discharged with a se-rum creatinine of 2 mg/dl; he was takingoral prednisolone (2 mg/kg per day),whichwas tapered over 2 weeks, followedby maintenance with oral mycopheno-late mofetil (750 mg/d).

A year later, the child was againadmittedwith similar complaints of feverand rash, although no focus of infectioncould be identified. Investigationsrevealed a rapid rise in serum creatinineto 4.4 mg/dl. The serum C3 level wasagain low normal (77.7 mg/dl) and

antinuclear antibody, ANCA, and viralmarkers were negative. A repeat renalbiopsy was performed with the clinicalsuspicionof a relapse.Thebiopsy showedsix glomeruli, three of which showedsegmental necrotizing lesions with cel-lular crescents similar to the previousbiopsy (Figure 2, A and B) along withacute tubular injury. There was no in-crease in tubulointerstitial chronicity.The tissue sent for IF contained renalmedullary tissue. IF performed afterproteinase K digestion of formalin-fixed,paraffin-embedded tissue showed coarsepredominantly capillary wall granular de-position of C3 (3+, 0–3+ scale) (Figure2C) with no staining for Igs.

The IF profile of “isolated C3” stainingprompted electron microscopy (EM),which to our surprise showed discontinu-ous intramembranous dense depositsalong with numerous irregularly placedsubepithelial andmesangial electrondensedeposits, classic for DDD. Secondary

podocyte damage with foot process ef-facement was also noted (Figure 2D).

Retrospectively, the biopsy from thefirst presentation was processed for EMand it too showed massive subepithelialand mesangial electron dense depositsalong with intramembranous deposits(Figure 1D). Thus, it was clear that bothbiopsies showed DDD with histologicappearance of a focal and segmental nec-rotizing crescentic GN, mimicking asmall vessel vasculitis.

The child was again started on pulsemethyl prednisolone (sixdoses) andplasmaexchanges (six alternate-dayexchanges).Heresponded to treatment, remained dialysisfree, and was discharged on prednisolone(60mg orally, once daily) andmycopheno-late (750mg).Hewas also given two dosesof rituximab (500 mg/dose) at weeklyintervals. The child remains in remission10 months later on the above regimen,with serum creatinine of 0.5 mg/dl, C3 of80 mg/dl, and a spot urine protein/creatinine ratio of 0.02. ELISA for anti–factor H antibody was negative.

DISCUSSION

GN with dominant C3 deposition, de-fined as C3c intensity two ormore ordersof magnitude greater than any otherimmune reactant (0–3 scale), has beenrecently termed C3 glomerulopathy.This new classification recognizes thefact that the glomerular morphology as-sociated with a dominant C3 IF profile isheterogenous (i.e., not always a mem-branoproliferative pattern of injury)and incorporates the entities of DDDand C3 GN. Correct identification ofthis group of GN is important becauseit suggests alternative complement path-way dysfunction and prompts investiga-tion of the complement system.3

The cause of underlying alternativepathway abnormality is also frequentlyheterogenous and may be genetic oracquired. Genetic abnormalities includehomozygous loss of function or heterozy-gous mutations of complement proteins(C3), complement regulatory proteins(complement factor H [CFH], comple-ment factor I [CFI], membrane cofactor

Figure 1. A case of DDD presenting as a crescentic necrotizing GN with isolated C3c de-position and intramembranous and subepithelial dense deposits. Renal biopsy at first pre-sentation. (A) A representative glomerulus with a segmental necrotizing lesion and overlyingcellular crescent (hematoxylin andeosin staining). (B) The discontinuities in the tuft (arrow) arehighlighted (silvermethenaminestaining)withsurroundingfibrindeposition. (C)There is focalC3c deposition (1+, 0–3+ scale) on IF (FITC-C3c staining). (D) Ultrastructural examinationshows intramembranous dense deposits in the GBM and Bowman’s capsule, with large ir-regular subepithelial deposits and foot process effacement (transmission EM, uranyl acetate-lead citrate). Original magnification, 320 in A–C; 31600 in D.

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protein, or CFH-related proteins 1–5), orpresence of their allelic variants. Particu-lar variants of CFH (exon 2 I62V, IVS2 218insTT, exon 9 Y402H, and exon10 A473A) and of CFHR5 (exon 2P46S,2249T.C and 220T.C) may prefer-entially be associated with DDD.4 Ac-quired abnormalities may occur becauseof the presence of autoantibodies (e.g., C3nephritic factor, anti–complement factorB, anti-CFI, anti-CFH, or anti-C3b) ordue to paraproteins, which may act asautoantibodies to these complementregulatory proteins.

It is important to note that C3glomerulopathy does not occur in allindividuals harboring risk alleles oreven mutations, possibly because ofunderlying control mechanisms. How-ever, an infectious trigger may over-whelm this compensatory mechanismand lead to deposition of alternatecomplement components in the glo-meruli, inciting various glomerular pat-terns of injury.5

Other differential diagnoses of a C3dominant IF profile include postinfec-tious GNand juvenile acute nonprolifer-ativeGN, discussed below.A small subsetof cases of postinfectious GN (C3 dom-inant immunostaining profile, subepi-thelial humps on EM) have an atypicalclinical course with persistent hypocom-plementemia, hematuria, or proteinuriaand progression to ESRD. Sethi et al.6

demonstrated alternate pathway abnor-mality in the form of CFH mutation,polymorphisms, and/or C3 nephriticfactor in 10 such patients.

In our patient, the C3 dominant IFprofile with intramembranous densedeposits by EM was consistent with thediagnosis of DDD; however, the histo-logic presentation was confounding. Afocal and segmental necrotizing patternofGNhas conventionally been attributedto a small vessel vasculitis–type injuryaffecting the GBM. Pathogenetically,this may be associated with ANCA vas-culitis, lupus nephritis, or HSN, all of

which may present with systemic fea-tures of a small vessel vasculitis.

Walker et al.2 identified four distincthistologic patterns of DDD, includingmesangial proliferative (45%), membra-noproliferative (25%), acute proliferative/exudative (12%) mimicking a postin-fectious GN, and crescentic overlying amesangioproliferative, membranopro-liferative, focal, or diffuse endocapillaryproliferative GN (18%). Two cases weredeemed unclassified with intermedi-ately electron dense transformation ofthe GBMs and mesangial region. Noneof the 81 cases in this series showed nec-rotizing glomerular lesions.

Similar to our case, Fervenza et al.7

described a 23-year-old man who pre-sented with fever, renal dysfunction, he-maturia, and low normal serum C3 andwas diagnosed with C3 GN with necro-tizing crescentic GN without evidenceof mesangial proliferation or a membra-noproliferative pattern of injury. Theauthors demonstrated a novel heterozy-gous factor H mutation (c.3350A.G inshort consensus repeat 19) along withrisk alleles (presence of two copies ofthe H402Y allele of CFH as well as twocopies of the G102 and one copy of theL314 alleles of C3). This factor H muta-tion was highly unusual, because muta-tions in short consensus repeat 19 areusually associated with atypical hemo-lytic uremic syndrome. The patient re-sponded to intravenous pulse steroidsand was in clinical remission on mainte-nance therapy with low-dose oral ste-roids 1 year after initial presentation.

As discussed by Fervenza et al.,7 in-terpretation of IF in such cases is a po-tential diagnostic pitfall and absence ofEM evaluation can result in a misdiag-nosis. Even in ANCA-associated GN,various authors have noted up to 2+staining (on a 0–4+ scale) of Igs or com-plement components. Thus, the termused for this group of lesions is “pauci-immune,” rather than “nonimmune.”8

The absence of ANCA in our patient,with the initial LM and IF findings sug-gestive of a pauci-immune crescenticGN, did not raise concerns because ap-proximately 20% of patients with pauci-immune GN are ANCA negative.9

Figure 2. Renal biopsy at the time of relapse. (A) Representative glomeruli with cellularcrescents.Note thepliable capillarywallswith absenceof remodelingand lackofproliferativeactivity (silver methenamine staining). (B) Segmental GBMdiscontinuities are noted in few ofthe glomeruli (arrow) (silver methenamine staining). (C) IF shows coarse granular C3c de-position (3+, 0–3+ scale) in the capillary walls (FITC-C3c staining). (D) Ultrastructural exami-nation shows intramembranous dense deposits with irregular subepithelial and mesangialdeposits, along with secondary foot process effacement (transmission EM, uranyl acetate-lead citrate). Original magnification, 310 in A and C; 360 in B;31000 in D.

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On review of the literature, both ofthese cases are reminiscent of the novelGN described by West et al.,9 originallyin 1978 and updated in 2000, termedjuvenile acute nonproliferative GN. Intheir series of 13 children (age at onsetwas consistently #12 years), the diseasewas characterized by sudden onset ofgross hematuria, rapid renal dysfunction,and slightly depressed or low normal se-rum C3. No hypertension or nephroticsyndrome was noted. History suggestiveof preceding infection including pharyn-gitis (n=3 cases), raised antistreptolysintiters or culture evidence of streptococ-cal infection (n=7 cases), or fever (n=11cases) was seen along with a rash in fourcases. On LM, crescents were present in80% of cases, with exudative responsein the underlying tuft, no or minimalmesangial matrix expansion, and occa-sional foci of fibrinoid necrosis (al-though less frequent than expected inan ANCA-associated GN). IF showedisolated C3 deposition. EM was charac-terized by subepithelial deposits on theparamesangial portion of the GBM,along with dense transformation of theGBM in three cases. Treatment withhigh-dose corticosteroids was highlysuccessful in this series. Relapses asso-ciated with infection or fever werenoted in five cases and one child had aspontaneous remission. Follow-upbiopsies at the time of a relapse had sim-ilar histologic findings without progres-sion of tubulointerstitial chronicity.The authors opined that rupture of theparamesangial portion of the GBMwhere large subepithelial deposits wereseen was responsible for florid crescentformation and renal failure. Althoughthis entity seemed similar to DDD onEM, the authors felt that the vastly dif-ferent clinical course in these patientsmade a case for a separate designationfor this disease.

With our newfound understanding ofcomplement abnormality, we hypothesizethat these cases may represent amilder formof C3 glomerulopathy (DDD/C3 GN)

not associated with severe complemen-temia or GBM remodeling. In the eventof an infectious trigger, the complementabnormality results in deposition of largesubepithelial complement-rich deposits,which weaken the paramesangial GBM,causing rupture, crescent formation(mimicking a small vessel vasculitis), andpresentation with renal failure. Treatmentwith steroids causes resolution of thesedeposits; however, relapses are frequentwith subsequent infections. These pa-tients do well on low-dose maintenanceimmunosuppression.

Therefore, the significance of this caseis that it adds to the histologic spectrumof DDD and provides an importantreminder that an isolated C3 IF profileshould always prompt further investiga-tion, including EM and complementstudies. We also propose that this casemay be part of a cohort within C3glomerulopathies with a distinct clinico-pathologic profile. Thesedistinct elementsinclude presentationwith renal failure andhematuria, possibly after infectious trig-ger; absence of hypertension, nephroticsyndrome, or severe hypocomplemen-temia, with a biopsy typically showingnecrotizing and crescentic GN withoutproliferation or evidence of remodeling;C3 dominant IF; and large subepithelialdeposits with or without dense trans-formation of the GBM. Most impor-tantly, patients with these features have afavorable clinical outcome and lack pro-gression to ESRD.

Recognitionof this entitywithdetailedstudy of the underlying complementabnormality is important to furtherour understanding of the spectrum ofcomplement-related glomerular diseases.

ACKNOWLEDGMENTS

We acknowledge Dr. Sanjeev Sethi for his

valuable opinion and Ram Singh and the EM

facility at All India Institute of Medical Sci-

ences for technical support.

DISCLOSURESNone.

REFERENCES

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