Identification of glomerular immune deposits in cryoglobulinemia glomerulonephritis

To provide further evidence of the nature of intraglomerular immune deposits in essential mixed cryoglobulinemia (EMC), we used two mouse monoclonal antibodies against cross-reactive idiotypes present on monoclonal rheumatoid factors (MoRFs) from patients with type II-EMC. MoAb Cc1 reacted with 9 of 16 circulating IgMk MoRFs tested, and MOAb Lc1 with four of the remaining. Using indirect immunofluorescence and immunoperoxidase techniques, we could identify the same cross-reactive idiotype of the serum MoRF in the renal biopsy specimens from 11 of 13 patients with EMC glomerulonephritis. Kidney specimens from the three patients, whose MoRF was not recognized by MoAbs Cc1 and Lc1, were negative. Two out of 30 control renal biopsies from patients with other forms of glomerulonephritis were shown to contain idiotype (Cc1 and Lc1) positive material. Both patients had serum polyclonal RF which could account for this finding. In conclusion, our results provide direct evidence that serum cryo-MoRF participate in the formation of glomerular immune deposits and, presumably, in the pathogenesis of renal damage in EMC glomerulonephritis.     

Recurrent essential mixed cryoglobulinemia in renal allografts. Report of two cases and review of the literature

This report describes two patients in whom essential IgG-IgM mixed cryoglobulinemia (EMC) glomerulonephritis led to end-stage renal disease. Both patients underwent primary hemodialysis, and during the period of uremia clinical and biological manifestations of the disease fully resolved. Transplantation was performed, and in both cases cryoglobulinemia quickly recurred (30 days and 6 months after transplantation, respectively) with clinical renal and extrarenal flare, and reappearance of the biological markers of the disease (decrease in C3 and C4 components of serum complement, detection of rheumatoid activity and of cryoglobulinemia in the serum). The literature on EMC glomerulonephritis leading to end-stage renal disease is reviewed. Factors that may have contributed to extinguishing the disease and to further recurrence following transplantation-consequences of uremic state, alloimmunization and intercurrent infectious disease-are discussed.     

Acquired and genetic complement abnormalities play a critical role in dense deposit disease and other C3 glomerulopathies

Dense deposit disease and glomerulonephritis with isolated C3 deposits are glomerulopathies characterized by deposits of C3 within or along the glomerular basement membrane. Previous studies found a link between dysregulation of the complement alternative pathway and the pathogenesis of these diseases. We analyzed the role of acquired and genetic complement abnormalities in a cohort of 134 patients, of whom 29 have dense deposit disease, 56 have glomerulonephritis with isolated C3 deposits, and 49 have primary membranoproliferative glomerulonephritis type I, with adult and pediatric onset. A total of 53 patients presented with a low C3 level, and 65 were positive for C3 nephritic factor that was significantly more frequently detected in patients with dense deposit disease than in other histological types. Mutations in CFH and CFI genes were identified in 24 patients associated with a C3 nephritic factor in half the cases. We found evidence for complement alternative pathway dysregulation in 26 patients with membranoproliferative glomerulonephritis type I. The complement factor H Y402H variant was significantly increased in dense deposit disease. We identified one at-risk membrane cofactor protein (MCP) haplotype for glomerulonephritis with isolated C3 deposits and membranoproliferative glomerulonephritis type I. Thus, our results suggest a critical role of fluid-phase alternative pathway dysregulation in the pathogenesis of C3 glomerulopathies as well as in immune complex-mediated glomerular diseases. The localization of the C3 deposits may be under the influence of MCP expression.     

Prevalence of hepatitis C virus—Associated mixed cryoglobulinemia after liver transplantation

Hepatitis C virus (HCV) infection is associated withmixed cryoglobulinemia and membranoproliferative glomerulonephritis. After orthotopic liver transplantation (OLT), isolated cases of HCV-associated mixed cryoglobulinemia have been reported. We determined the prevalence and clinical characteristics of mixed cryoglobulinemia in HCVinfected liver transplant recipients at our institution. Between January 1991 and February 1998, a total of 191 OLTs were performed in 178 patients. Among these transplant recipients, 53 patients (29.8%) had positive serological test results for HCV infection by second-generation enzyme-linked immunosorbent assay. We studied 31 HCVpositive (HCV+) and 21 HCV-negative (HCV-) transplant recipients (control group). Renal and liver function studies were performed, and cryoglobulin, rheumatoid factor, C3, C4, and serum HCV RNA levels and genotype were determined. Results were compared using unpaired Student's t-test for continuous variables and Fisher's exact test for categorical variables. Baseline characteristics were similar between the groups. Six patients in the HCV+ group (19%) had mixed cryoglobulins present at the time of evaluation compared with none in the HCV- group (P = .036). The only parameter associated with cryoglobulins in the HCV+ group was rheumatoid factor (P < .01). In 3 HCV+ patients with cryoglobulins, extrarenal signs of cryoglobulinemia were present. Glomerulonephritis was found in 4 HCV+ patients. Two patients with purpura and cryoglobulinemia had reduced clinical manifestations after antiviral therapy. In conclusion, mixed cryoglobulinemia was found in approximately 20% of the HCV+ liver transplant recipients. The presence of purpura or glomerulonephritis suggests HCV-associated mixed cryoglobulinemia, a clinical syndrome that may respond favorably to antiviral therapy.     

Kidney and liver involvement in cryoglobulinemia

Cryoglobulinemia is a pathological condition characterized by the presence in the blood of a group of proteins (cryoglobulins) showing the common property of precipitating from cooled serum. Mixed cryoglobulins (MCs) are composed of a polyclonal immunoglobulin G (IgG) bound to another immunoglobulin that acts as an anti-IgG rheumatoid factor; 2 types of MCs can be identified. The origin is not clear in 30% of all MCs, and this subset of cryoglobulinemias is called "essential." The great majority (up to 90%) of patients with essential MC (EMC) of both types has been related to HCV infection. The renal involvement in essential MC has been observed in 2% to 50% of patients in reported series. A well-characterized pattern of glomerular disease termed "cryoglobulinemic glomerulonephritis" is present in individuals with type-II EMCs in serum and IgMk RF being the most frequent monoclonal component. Aspecific and infrequent glomerular lesions occur in EMC patients with type III cryoglobulins. The most frequent histologic picture of cryoglobulinemic GN is that of membranoproliferative GN (MPGN) with subendothelial deposits. However, cryoglobulinemic GN may have some distinctive features that differentiate it from idiopathic type-I MPGN. Evidence of liver involvement has been found in 60% to 80% of EMC patients. Recent data support the notion that the stage of liver disease in patients with type II or III MC has association with the prevalence of cryoglobulinemia. Few controlled trials have been published on the treatment of HCV-related MC; in addition, the majority of the patients enrolled in these trials had an unclear renal involvement. Interferon (IFN) is an effective drug for the treatment of patients with HCV-associated MC and cryoglobulinemic GN. In the presence of acute cryoglobulinemic GN, IFN does not prevent progression of renal damage; combination therapy with cytotoxic ad anti-inflammatory drugs, and sometimes plasma exchange, is recommended. Prospective controlled trials are underway on this purpose.     

Membranous glomerulonephritis in rheumatoid arthritis not related to gold or D-penicillamine therapy: a report of four cases and review of the literature

In a series of 96 patients with membranous glomerulonephritis (MGN) there were 14 who had concomitant rheumatoid arthritis. Ten of these had been treated with gold or D-penicillamine; in four patients neither of these drugs could have been responsible for the MGN. One of them received intrasynovial osmium tetroxide two months before the clinical onset of MGN. Three of the patients had positive rheumatoid factor. HLA-type was examined in three patients and all showed B27 antigen but not DR3. No patient developed signs of systemic lupus erythematosus during the follow-up (mean 5.9 years). In two patients MGN persisted as judged from urinary abnormalities, one patient recovered after a relapse period and one developed secondary amyloidosis.     

Pauci-immune necrotizing glomerulonephritis complicating rheumatoid arthritis

Necrotizing glomerulonephritis associated with rheumatoid arthritis typically occurs in the setting of frankly apparent systemic vasculitic signs and symptoms. We report two recent cases that differed from this paradigm. Both patients had rheumatoid arthritis and deteriorating renal function due to P-ANCA positive pauci-immune necrotizing crescentic glomerulonephritis, but minimal systemic symptoms. Delay in diagnosis and institution of appropriate therapy may have contributed to the dialysis dependence of one of these patients. We suggest that heightened suspicion of an aggressive necrotizing glomerulonephritis should be maintained in all patients with rheumatoid arthritis who present with acute renal insufficiency even in the absence of frank vasculitis.     

Development of glomerulonephritis during anti-TNF-alpha therapy for rheumatoid arthritis.

BACKGROUND: Treatment of rheumatoid arthritis with anti-tumour necrosis factor alpha (TNFalpha) agents may lead to autoantibody formation and flares of vasculitis, but renal complications are rare. METHODS: We report the clinical and pathologic findings in five patients with longstanding rheumatoid arthritis (duration of rheumatoid arthritis, 10-30 years; mean, 23 years) who developed new onset of glomerular disease after commencing therapy with anti-TNFalpha agents (duration of therapy, 3-30 months; median, 6 months). RESULTS: At presentation, three patients were receiving etanercept, one adalimumab and one infliximab. Two subjects presented with acute renal insufficiency, haematuria, nephrotic-range proteinuria, positive lupus serologies, and hypocomplementemia, and renal biopsies showed proliferative lupus nephritis. Two individuals presented with new onset renal insufficiency, haematuria and proteinuria, and renal biopsies showed pauci-immune necrotizing and crescentic glomerulonephritis. One of these subjects, who had anti-myeloperoxidase autoantibodies, also developed pulmonary vasculitis. The fifth patient presented with nephrotic syndrome and renal biopsy findings of membranous glomerulonephritis, associated with immune complex renal vasculitis. A pathogenic role for anti-TNFalpha therapy is suggested by the close temporal relationship with development of glomerular disease, and by the improvement in clinical and laboratory abnormalities after drug withdrawal and initiation of immunosuppressive therapy in most cases. CONCLUSIONS: Rheumatoid arthritis patients receiving anti-TNFalpha agents may develop glomerulonephritis via the induction of rheumatoid arthritis-related nephropathy or de novo autoimmune disorders.     

Nephritic factor and recurrence in the renal transplant of membranoproliferative glomerulonephritis type II

Animal models suggest a role for nephritic factor in the pathogenesis of glomerular disease, but evidence for a role in human disease is lacking. To assess its role, we applied a recently developed method that allows measurement of low levels of nephritic factor activity to stored serum specimens from three patients who had membranoproliferative glomerulonephritis (MPGN) type II. All three had had renal transplants, and one lost two of three transplants from recurrent disease. Evidence for a role for nephritic factor in human disease was a positive correlation between the level of nephritic factor activity and both the severity of recurrence and an increase in serum creatinine concentration. However, the hypocomplementemia was never severe; C3 levels of 49-76 mg/dl and nephritic factor levels of 89 U/ml were associated with severe recurrences. We have previously seen severe disease with mild hypocomplementemia. In contrast, patients with partial lipodystrophy often have severe hypocomplementemia and, presumably, high levels of nephritic factor yet have a mild glomerulonephritis. Disease severity and nephritic factor levels thus appear to be inversely related. The disease is progressive when only moderate amounts of nephritic factor have been circulating and C3 only mildly depressed.     

Nail fold videocapillaroscopy in mixed cryoglobulinaemia.

BACKGROUND: Nail fold videocapillaroscopy (NVC) has been extensively used to examine morphological and functional changes of microcirculation in connective tissue diseases. The nutritional circulation that depends on tissue capillaries, can be expected to be significantly impacted in mixed cryoglobulinaemia (MC). METHODS: Using NVC, we evaluated 29 patients with MC (19 women), mean age 66 years (range 40-83). They included 28 hepatitis C virus (HCV) positive patients-14 genotype 1b, 10 genotype 2a 2c, two genotype 4, two with undetermined genotype. Of them, 18 had type II (IgMk-IgG) MC and 11 had type III. All patients were symptomatic, presenting with weakness (24 of 29 patients), arthralgia (24), purpura (16), peripheral neuropathy (20), Raynaud's phenomenon (8), hypertension (19) and membranoproliferative glomerulonephritis (MPGN) (9). The nail fold capillaries of four fingers per hand were examined using a videomicroscope. RESULTS: Of the 29 patients, 27 had morphological abnormalities (including tortuosity and apical enlargement), 18 had capillaries with deeply altered orientations, 17 had shortened capillaries and 20 neoangiogenetic phenomena. These four types of capillary abnormalities were simultaneously present in 10, suggesting this combination to be a characteristic pattern in MC. Less common alterations included haemorrhages (10 cases), enlarged and giant capillaries (2) and avascular areas (2). The patients with MC-associated MPGN had a significantly greater number of capillary abnormalities (mean 4.5, range 4-6) than non-nephritic patients (mean 3.5, range 1-6, P = 0.01). The number of capillary abnormalities was not related to the presence of Raynaud's phenomenon. Microcirculatory changes did not correlate with other clinical manifestations or serological indices, including cryocrit, cryoglobulin type, HCV genotype, viral load, haemoglobin, ALT, rheumatoid factor, IgM and C4 levels. CONCLUSIONS: Patients with MC show a variety of microcirculatory changes, often clustered in a characteristic pattern of abnormally oriented, short capillaries and neoangiogenetic phenomena. Capillary changes are more numerous in nephritic patients.     

Circulating immune-complexes and complement activation through the classical pathway in myeloperoxidase-ANCA-associated glomerulonephritis

BackgroundAnti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (AAGN) is the fulminant glomerular diseases with poor renal prognosis. Activation of the complement system has recently been reported in the pathogenesis of AAGN, but it remains to be clarified as to which complement pathway is mainly involved.Methods20 patients with myeloperoxidase (MPO)-AAGN were retrospectively evaluated. Using serum samples, circulating immune-complexes (CICs) were assessed by the monoclonal rheumatoid factor assay, and C5a and C5b-9 were assessed by ELISA. Complement activation through the classical pathway was further evaluated by the WIESLAB® Complement System Classical Pathway kit. The affinities of ANCAs were evaluated by a competitive inhibition method using ELISA, and were classified into the high, and low-affinity group. Deposition of complement components, such as C3, C5, C4d, C5b-9, factor Bb, mannan-binding lectin serine peptidase (MASP)-1, MASP-2, and mannose/mannan-binding lectin (MBL), in frozen renal sections were analyzed by immunofluorescence staining.ResultsCICs were found to be positive in 65% of the patients. All CIC-positive patients belonged to the high-affinity group. Furthermore, serum C5a and C5b-9 were significantly increased in MPO-AAGN patients, and these levels positively correlated with CIC levels. A significant negative correlation was also found between levels of WIESLAB® classical pathway kit and CICs. By immunofluorescence staining, glomerular deposition of C4d, C5, and C5b-9 were observed in similar distributions in MPO-AAGN patients, whereas the deposition of MASP-1, MASP-2, MBL, and factor Bb were minimal.ConclusionsThese results suggest the involvement of immune-complex induced complement activation through the classical pathway in the pathogenesis of MPO-AAGN.     

Necrotizing glomerulonephritis in rheumatoid arthritis

Rheumatoid arthritis may be associated with several glomerular lesions including amyloidosis, mesangial proliferation and membranous glomerulonephritis. Systemic vasculitis is a well-recognized extra-articular complication of rheumatoid arthritis, but necrotizing glomerulonephritis, the glomerular expression of vasculitis, has been described infrequently. This report comprises four patients with rheumatoid arthritis who underwent renal biopsy for declining renal function, proteinuria and active urine sediments. Pathology revealed that three patients had segmental necrotizing glomerulonephritis without significant glomerular immunoglobulin deposition. The fourth had segmental necrosis associated with diffuse membranous glomerulonephritis. We conclude that necrotizing glomerulonephritis is part of the spectrum of glomerular lesions seen in patients with rheumatoid arthritis. Because of therapeutic considerations involving the use of cyclophosphamide, necrotizing glomerulonephritis should be a diagnostic consideration in the rheumatoid arthritis patient with signs of glomerulonephritis and rapidly deteriorating renal function.     

Association of overt glomerulonephritis and liver disease: a study of 34 patients.

Thirty-four patients with overt glomerulonephritis and chronic liver disease were studied. Kidney specimens were examined by light, electron and immunofluorescence microscopy. Plasma C3 levels were measured and a search for cryoglobulinemia was carried out in all patients. Twenty-six out of the thirty-four patients had an immune complex type glomerulonephritis (membrano-proliferative glomerulonephritis or glomerulosclerosis with mesangial deposits) suggestive of hepatic glomerulonephritis. The glomerular deposits almost always contained IgA and very frequently other immunoglobulins as well as C3. The membrano-proliferative glomerulonephritis was characterized by severe renal symptoms, mixed cryoglobulinemia and the frequent finding of low C3 levels. These data suggest that there is a linkage between liver disease and glomerulonephritis. The immunomorphological type of glomerulonephritis and the cryoglobulinemia are both suggestive of an immune complex disease. The lowering of the C3 levels could be due to activation of complement components by immune complexes, to hepatic hyposynthesis, or to a combination of the two.     

12例C3肾小球肾炎的临床病理特点及其血浆补体活化分析

目的 研究新命名的C3肾小球肾炎的临床和病理特点,明确血浆补体活化状况及其与临床的相关性。 方法 回顾性分析我科1999年1月至2010年6月符合最新C3肾小球肾炎定义的12例患者的临床病理资料,区分为膜增生型（MPGN）和非MPGN型。测定肾活检当天血浆部分补体成分水平以明确补体活化途径,分析补体活化产物与临床的相关性。 结果 12例患者中10例为非MPGN型,2例为MPGN型。所有患者均有蛋白尿。10例非MPGN型中2例为肾病水平蛋白尿,6例伴镜下血尿,1例伴肉眼血尿,2例伴肾功能减退。2例MPGN型中1例为肾病水平蛋白尿,伴镜下血尿、高血压、肾功能减退;另1例为单纯蛋白尿,伴高血压,而肾功能正常。所有患者血浆C3均在正常范围,但血浆B因子水平显著低于健康对照组（n=10）,Ba、C3a、C4a和C5a水平均显著高于健康对照组。血浆Ba水平与尿蛋白量呈正相关;而C3a、C4a、C5a与尿蛋白量、Scr无相关。非MPGN型C3肾小球肾炎多表现为轻度系膜增生,4例患者出现不同程度新月体。MPGN型则与I型MPGN类似,其中1例47.1%肾小球出现新月体。 结论 本组C3肾小球肾炎中以非MPGN型为主;临床上多表现为肾炎综合征;病理多表现为轻度系膜增生性肾小球肾炎。补体旁路活化在C3肾小球肾炎中可能发挥重要作用。     

Mixed cyroglobulinaemia, glomerulonephritis, and ANCA: essential cryoglobulinaemic vasculitis or ANCA-associated vasculitis?

Antineutrophil cytoplasmic antibodies (ANCA) are generally believed to be strongly associated with some primary systemic vasculitides (PSV), such as Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), and Churg-Strauss syndrome (CSS), which have some clinical manifestations in common and are 'pauci-immune' by immunohistology. This group of PSV has thus been termed 'ANCA-associated vasculitis' (AAV). By contrast, essential mixed cyroglobulinaemic vasculitides (EMC) are clinically heterogeneous and characterized immunologically by complement consumption and by immunocomplex depositions; they are also characteristically ANCA-negative. We report here on two SV-patients in whom the detection of cANCA (proteinase 3-ANCA in one case) in conjunction with glomerulonephritis and various extrarenal vasculitic lesions was suggestive of an AAV. However, demonstration of type II cryoglobulinaemia in conjunction with hypocomplementaemia, and histological proof of immunocomplexes in the glomerulus led to the diagnosis of an EMC, which was associated with hepatitis C virus (HCV) infection in one of the cases. Against the setting of 'false positive' cANCA in EMC, we discuss the differential diagnostic steps as well as current differential therapeutic approaches. Key words: glomerulonephritis; hepatitis; interferon-&agr; mixed cyroglobulinaemia; ANCA; vasculitis      

Temporal arteritis with pauci-immune glomerulonephritis: a systemic disease

Temporal arteritis is easily diagnosed and responds gratifyingly to treatment. Renal complications are unusual, but nevertheless occur. Earlier, an association between pauci-immune glomerulonephritis and temporal arteritis was shown. We present a patient who clearly had temporal arteritis but also developed cerebral hemorrhage, pulmonary infiltrates related to granulomatous pulmonary vasculitis, and pauci-immune glomerulonephritis. We suggest that temporal arteritis is neither always localized nor temporal. Instead, the condition can be a lethal, systemic disease. Renal involvement in patients with temporal arteritis is not common and the presence of glomerulonephritis is rare [Jennette and Falk 1994]. Lenz et al. [1998] described a patient who developed vision loss, optic nerve atrophy, elevated erythrocyte sedimentation rate, a positive rheumatoid factor and terminal glomerulonephritis. The renal biopsy showed focal and segmental necrotizing glomerulonephritis, despite negative antineutrophil cytoplasmatic antibodies (ANCA), antinuclear antibodies and antiglomerular basement membrane antibodies. Giant cells were identified in the necrotic vessel walls within the kidney. Immunofluorescence was negative and a diagnosis of ANCA-negative pauci-immune glomerulonephritis was made. The patient did not respond to immunosuppression and developed end-stage renal disease. Although the clinical attributes were consistent with temporal arteritis, no temporal artery biopsy was done in that patient. We recently treated a patient with temporal arteritis and pauci-immune glomerulonephritis. Our patient's course was somewhat different in comparison to the patient described by Lenz et al. [1998].     

Myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-positive microscopic polyarteritis (MPA) associated with Hashimoto's thyroiditis and increased serum rheumatoid factor

An autopsy case of microscopic polyarteritis (MPA) associated with Hashimoto's thyroiditis that showed glomerular immunoglobulin and complement depositions and high titers of rheumatoid factor and myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) is reported. A 72-year-old woman was admitted to our hospital because of renal failure that had deteriorated from a serum creatinine value of 175.8 to 1874.1 μmol/l in 4 weeks. Laboratory studies on admission revealed proteinuria, numerous red blood cells, granular casts and red blood casts in the urine, increased serum blood urea nitrogen (47.8 mmol/l), anemia (hemoglobin, 60 g/l), and thrombocytopenia (platelets, 71 × 10⁹/l). Emergency hemodialysis was started; however, the patient died on the fifth hospital day because of ventricular tachycardia, and an autopsy was performed. At autopsy, the patient was found to have had increased serum levels of immune complexes, rheumatoid factor, IgG rheumatoid factor, myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), anti-thyroglobulin antibody, and anti-thyroid peroxidase antibody, and decreased serum complement levels. Microscopic examination revealed crescentic glomerulonephritis in almost all glomeruli, and positive granular deposits of IgG, IgA, IgM, C1q, C3, and C4 in the mesangium and along the capillary walls. Typical fibrinoid necrosis was found in the small arteries of the stomach, colon, small intestine, and bladder. Finally, Hashimoto's thyroiditis was noted. To our knowledge, this is the first case of MPO-ANCA-positive MPA associated with Hashimoto's thyroiditis and increased serum rheumatoid factor levels. Received: February 9, 2000 / Accepted: July 4, 2000     

Glomerular paramesangial deposits: association with hypocomplementemia in membranoproliferative glomerulonephritis types I and III

Of 22 subjects previously reported with some form of factor H dysfunction, 12 had a glomerulonephritis that appeared to not be of immune complex origin. Factor H dysfunction results in elevated circulating levels of the C3b-dependent C3 convertase, C3b,Bb. Of the 12 cases with glomerulonephritis, the glomerular deposits in the six whose biopsy specimens were studied were predominately subepithelial on the paramesangial portion of the glomerular basement membrane. In a subsequent study, similar deposits were found in patients with membranoproliferative glomerulonephritis (MPGN) type II, also a nephritis that is probably not of immune complex origin. Paramesangial deposits were found in these patients only in biopsy specimens obtained when the C3 level was low, at which time convertase stabilized by nephritic factor would be present in the circulation. This association of paramesangial deposits with circulating convertase was further tested by correlating these deposits with the level of C3 at the time of biopsy in MPGN types I and III. The results in type III MPGN were similar to those in type II; paramesangial deposits were frequently present when the C3 level was low as a result of circulating nephritic factor of the terminal pathway, NFt, and were usually absent when the C3 level was in the upper two thirds of the normal range. Deposits persisted in those patients with C3 levels that had been low but that had increased during the year before biopsy to within the lower one third of the normal range. The persistence of paramesangial deposits in MPGN type III, as compared with MPGN type II, may be related to the differences in composition and function of the two NF stabilized convertases (C3bn,Bb,P,NFt and C3b,Bb,NFa, respectively) that circulate in these two disorders. In contrast to MPGN type III, the hypocomplementemia in MPGN type I is thought to be, for the most part, the result of classical pathway activation, which is not associated with elevated circulating convertase levels. In agreement with this, paramesangial deposits were found in only two of 34 biopsy specimens. At the time of those two biopsies, both patients had a complement profile indicating that the NFt was circulating, as in MPGN type III. In three other cases with profiles compatible with circulating NFt, paramesangial deposits were not found. In all patients with type I MPGN, electron microscopy and immunofluorescence of the glomeruli gave results typical of an immune complex nephritis. Thus, even though the complement profile in MPGN type I may at times indicate the presence of a nephritic factor, circulating immune complexes appear to be basic to pathogenesis. The observations support the hypothesis that elevated levels of the C3b-dependent convertase, as found in the "experiments of nature" with factor H dysfunction and in MPGN types II and III, are associated with paramesangial deposits. The nature of this association and the role of these deposits in producing the nephritis is not clear.     

Nephropathy associated with heroin abuse in Caucasian patients.

BACKGROUND: Renal disease is a complication of heroin addiction. Using renal biopsies in Caucasian patients, we studied the types of nephropathy associated with heroin abuse. METHODS: Nineteen renal biopsies were performed on heroin addicts between January 1993 and December 2001. The indications for renal biopsy included proteinuria with or without renal insufficiency. RESULTS: All 19 patients had serological evidence of hepatitis C virus (HCV) infection, one had hepatitis B virus surface antigen and three were HIV positive. Thirteen patients (68.4%) were found to have membranoproliferative glomerulonephritis (MPGN), 12 with type I and one with type III. Of the remaining patients, two had chronic interstitial nephritis, two had acute proliferative glomerulonephritis, one had amyloidosis and one had granulomatous glomerulonephritis with interstitial nephritis. No apparent decline in the incidence of renal disease was observed. CONCLUSIONS: In this cohort of male Caucasian heroin addicts, HCV-associated MPGN was the most frequent pattern of nephropathy, showing that the nephropathy associated with heroin abuse in Caucasians is not of the focal and segmental glomerulosclerosis type, in contrast to previous reports on African-Americans. This aspect may have important implications for patient management and prognosis.     

Dense intramembranous deposit disease: new pathologic features

The pathologic and clinical features of 16 patients with dense intramembranous deposit disease are described. By light microscopy nine patients had membranoproliferative glomerulonephritis, five had focal segmental necrotizing glomerulonephritis with segmental epithelial crescents, four of whom also had a prominent tubulointerstitial nephritis, and two had focal segmental mesangial proliferative glomerulonephritis. The patients with membranoproliferative glomerulonephritis and one with focal segmental mesangial proliferative glomerulonephritis had easily recognizable dense intramembranous deposits by optical microscopy. The patients with focal segmental necrotizing glomerulonephritis and one with focal segmental mesangial proliferative glomerulonephritis did not have recognizable peripheral loop dense intramembranous deposits even under oil immersion. In patients with membranoproliferative glomerulonephritis ultrastructural examination revealed extensive capillary wall dense intramembranous deposits. Immunofluorescence revealed diffuse double linear staining along the capillary walls and "mesangial rings" of C3. In the patients with focal segmental necrotizing glomerulonephritis and one with focal segmental mesangial proliferative glomerulonephritis the immunofluorescence study suggested a diagnosis of dense intramembranous deposit disease because of the segmental double linear staining of the capillary walls and "mesangial rings" of C3, but the diagnosis was only established by fine structural analysis where occasional peripheral loop and prominent paramesangial basement membrane dense intramembranous deposits and mesangial nodular deposits were identified. Clinical features prior to biopsy included nephrotic syndrome in eight patients, an acute nephritic syndrome in six patients, and asymptomatic proteinuria and hematuria in two patients. Five of six patients with an acute nephritic presentation had focal segmental necrotizing glomerulonephritis. The acute renal insufficiency in these patients was transitory and appeared to be related to a prominent acute tubulointerstitial nephritis present in four of the biopsy specimens. Depressed serum C3 levels were present in patients with membranoproliferative glomerulonephritis; patients with focal segmental lesions were normocomplementemic. Because of the "atypical" light microscopic features in six of our patients, we support the suggestion that membranoproliferative glomerulonephritis, type II be replaced by the term 'dense intramembranous deposit disease' for this glomerulopathy with variable clinical and histologic features.