Non-crystalline light chain proximal tubulopathy, a morphologically protean entity

BACKGROUND

Light chain proximal tubulopathy (LCPT) is a rare form of paraprotein-related disease, occurring in two main histopathological forms: crystalline and non-crystalline. The clinicopathological features, treatment strategies and outcomes, especially of the non-crystalline form, are not well described.

METHODS

We conducted a single-centre retrospective case series of 12 LCPT patients, 5 crystalline and 7 non-crystalline, between 2005 and 2021.

RESULTS

The median age was 69.5 years (range 47-80). Ten patients presented with CKD and significant proteinuria (median estimated glomerular filtration rate of 43.5 ml/min/1.73 m2; urine protein:creatinine ratio 328 mg/mmol). Only six patients had known haematological disease at the time of renal biopsy. Multiple myeloma (MM) was diagnosed in seven patients cases and monoclonal gammopathy of renal significance (MGRS) in five patients. A clone was detected in all cases combining serum/urine electrophoresis and free light chain (LC) assays. Crystalline and non-crystalline variants had similar clinical presentations. For the non-crystalline variant, a diagnosis was reached based on a combination of CKD without another cause, haematological workup, LC restriction on immunofluorescence and abnormalities on electron microscopy (EM). Nine of 12 patients received clone-directed treatment. Patients who achieved haematological response (including all non-crystalline LCPT) had improved renal outcomes over a median follow-up of 79 months.

CONCLUSIONS

The non-crystalline variant may go unrecognised because of its subtle histopathological features and requires EM to distinguish it from 'excessive LC resorption without tubular injury'. Clone-directed treatment with good haematological response improves renal outcomes in both variants but limited data exist in MGRS. Multicentre prospective studies are needed to better define the clinicopathological characteristics associated with poor outcomes and optimize treatment strategies in patients with MGRS.

Combination treatment with rituximab, low-dose cyclophosphamide and plasma exchange for severe antineutrophil cytoplasmic antibody-associated vasculitis

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis can present with life-threatening lung-kidney syndromes. However, many controlled treatment trials excluded patients with diffuse alveolar hemorrhage or severely impaired glomerular filtration rates, and so the optimum treatment in these cases is unclear. In this retrospective cohort study, we report the outcomes of 64 patients with life-threatening disease treated with a combination regimen of rituximab, low-dose intravenous cyclophosphamide, oral glucocorticoids, and plasma exchange. At entry, the median estimated glomerular filtration rate was 9 mL/min, 47% of patients required dialysis, and 52% had diffuse alveolar hemorrhage. All patients received a minimum of seven plasma exchanges, and the median cumulative doses of rituximab, cyclophosphamide, and glucocorticoid were 2, 3, and 2.6 g, respectively, at six months. A total of 94% of patients had achieved disease remission (version 3 Birmingham Vasculitis Activity Score of 0) at this time point, and 67% of patients who required dialysis recovered independent kidney function. During long-term follow-up (median duration 46 months), overall patient survival was 85%, and 69% of patients remained free from end-stage kidney disease, which compares favorably to a historic cohort with severe disease treated with a conventional induction regimen. Combination treatment was associated with prolonged B cell depletion and low rates of relapse; 87% of patients were in continuous remission at month 36. The serious infection rate during total follow-up was 0.28 infections/patient/year, suggesting that combination treatment is not associated with an enduring risk of infection. Thus, we suggest that combination immunosuppressive therapy may permit glucocorticoid avoidance and provide rapid and prolonged disease control in patients with severe ANCA-associated vasculitis.

The mixed reality medical ward round with the MS HoloLens 2: Innovation in reducing COVID-19 transmission and PPE usage

Background

The COVID-19 pandemic necessitated changes to the traditional medical ward round to protect staff and patients. This study investigated the value and acceptability of using the Microsoft HoloLens 2 mixed reality headset in a COVID-19 renal medicine ward.

Methods

The HoloLens 2 was used during the height of the COVID-19 pandemic and it was compared with the days prior to its introduction. Staff exposure to COVID-19 and PPE usage were measured, and staff and patients were surveyed on the HoloLens 2 experience.

Results

The average ward round was significantly shorter with the use of the HoloLens 2 (94 minutes vs 137 minutes; p=0.006). With the HoloLens 2, only the consultant was in direct contact with COVID-19 patients compared with up to seven staff members on a normal ward round. Personal protective equipment usage was reduced by over 50%. Both staff and patients were positive about its use but raised some important concerns.

Conclusion

The HoloLens 2 mixed reality technology is an innovative solution to the challenges posed by COVID-19 to the traditional medical ward round.

Membranous nephropathy associated with viral infection

Background

Membranous nephropathy (MN) can be associated with hepatitis infection and less commonly with human immunodeficiency virus (HIV) infection. The significance of anti-phospholipase A2 receptor (PLA2R) and anti-thrombospondin type 1 domain-containing 7A (THSD7A) antibodies in this setting is unclear.

Methods

We describe the clinical, histopathological and outcome data of 19 patients with MN and hepatitis B virus (HBV), hepatitis C virus (HCV) or HIV infection identified through our renal biopsy database and the association with anti-PLA2R antibodies and anti-THSD7A antibodies.

Results

The cohort consisted of 19 patients, 8 male and 11 female, with a median age of 42 years (range 23–74). HBV infection was found in six cases, HCV in four and HIV in nine (two HIV patients had HBV co-infection and one HCV co-infection). PLA2R staining on biopsy was positive in 10/19 patients: 4 with HBV-MN, 3 with HCV-MN and 3 with HIV-MN and circulating anti-PLA2R antibodies were detected in 7/10 cases. THSD7A staining on biopsy was positive in three PLA2R-negative cases, one with HBV-MN and two with HIV-MN. Mean proteinuria was higher in the PLA2R-positive group and the median urinary protein:creatinine ratio (uPCR) was 963 mg/mmol (range 22–2406) compared with the PLA2R-negative group [median uPCR 548 mg/mmol (range 65–1898); P = 0.18 Mann–Whitney]. Spontaneous remission occurred in 6/19 patients and after-treatment remission occurred in 7/11 patients. Renal function was preserved in all but two patients who required haemodialysis 2 and 11 years from diagnosis.

Conclusions

We describe a cohort of patients with MN associated with viral infection, including rare cases of HIV-MN with PLA2R and THSD7A positivity. The mechanism of coincidental or viral-related MN needs to be investigated further.

Fluorodeoxyglucose Positron Emission Tomography Detects the Inflammatory Phase of Sclerosing Peritonitis

Objective

We studied the effectiveness of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in detecting inflammation in known or suspected cases of sclerosing peritonitis in patients on peritoneal dialysis (PD).

Design

We undertook FDG-PET scanning in PD patients presenting with symptoms or signs suggestive of sclerosing peritonitis (SP), and in patients on long-term PD with no symptoms of SP.

Setting

The study was performed in a PD unit in a tertiary-care hospital.

Patients and Methods

Three patients with known or strongly suspected SP underwent FDG-PET scans, 1 within 3 months of presentation with symptoms and 2 who were scanned more than 9 months after presentation. One patient was scanned at an early and a late time point. Five patients who had been on PD for more than 5 years and who were asymptomatic also underwent FDG-PET scanning. Scans were interpreted by a specialist in nuclear medicine.

Results

The scan performed in the early stages of SP showed increased peritoneal uptake. However, three scans taken more than 9 months after presentation with suspected SP showed mild peritoneal abnormalities only. One of 5 asymptomatic long-term PD patients showed increased peritoneal uptake associated with loss of ultrafiltration and high transporter status.

Conclusions

FDG-PET scanning may be a useful adjunct in the diagnosis of the acute phase of SP. More study is needed to define its role in the diagnosis of SP in asymptomatic PD patients.

Randomized, Controlled Trial of Tacrolimus and Prednisolone Monotherapy for Adults with De Novo Minimal Change Disease: A Multicenter, Randomized, Controlled Trial

BACKGROUND AND OBJECTIVES

Minimal change disease is an important cause of nephrotic syndrome in adults. Corticosteroids are first-line therapy for minimal change disease, but a prolonged course of treatment is often required and relapse rates are high. Patients with minimal change disease are therefore often exposed to high cumulative corticosteroid doses and are at risk of associated adverse effects. This study investigated whether tacrolimus monotherapy without corticosteroids would be effective for the treatment of de novo minimal change disease.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a multicenter, prospective, open-label, randomized, controlled trial involving six nephrology units across the United Kingdom. Adult patients with first presentation of minimal change disease and nephrotic syndrome were randomized to treatment with either oral tacrolimus at 0.05 mg/kg twice daily, or prednisolone at 1 mg/kg daily up to 60 mg daily. The primary outcome was complete remission of nephrotic syndrome after 8 weeks of therapy. Secondary outcomes included remission of nephrotic syndrome at 16 and 26 weeks, rates of relapse of nephrotic syndrome, and changes from baseline kidney function.

RESULTS

There were no significant differences between the tacrolimus and prednisolone treatment cohorts in the proportion of patients in complete remission at 8 weeks (21 out of 25 [84%] for prednisolone and 17 out of 25 [68%] for tacrolimus cohorts; P=0.32; difference in remission rates was 16%; 95% confidence interval [95% CI], -11% to 40%), 16 weeks (23 out of 25 [92%] for prednisolone and 19 out of 25 [76%] for tacrolimus cohorts; P=0.25; difference in remission rates was 16%; 95% CI, -8% to 38%), or 26 weeks (23 out of 25 [92%] for prednisolone and 22 out of 25 [88%] for tacrolimus cohorts; P=0.99; difference in remission rates was 4%; 95% CI, -17% to 25%). There was no significant difference in relapse rates (17 out of 23 [74%] for prednisolone and 16 out of 22 [73%] for tacrolimus cohorts) for patients in each group who achieved complete remission (P=0.99) or in the time from complete remission to relapse.

CONCLUSIONS

Tacrolimus monotherapy can be effective alternative treatment for patients wishing to avoid steroid therapy for minimal change disease.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2020_01_16_CJN06180519.mp3.

A novel glucocorticoid-free maintenance regimen for anti-neutrophil cytoplasm antibody-associated vasculitis

Objectives

Glucocorticoids (GCs) are a mainstay of treatment for patients with ANCA-associated vasculitis (AAV) but are associated with significant adverse effects. Effective remission induction in severe AAV using extremely limited GC exposure has not been attempted. We tested an early rapid GC withdrawal induction regimen for patients with severe AAV.

Methods

Patients with active MPO- or PR3-ANCA vasculitis or ANCA-negative pauci-immune glomerulonephritis were included. Induction treatment consisted of two doses of rituximab, 3 months of low-dose CYC and a short course of oral GC (for between 1 and 2 weeks). Clinical, biochemical and immunological outcomes as well as adverse events were recorded.

Results

A total of 49 patients were included, with at least 12 months of follow-up in 46. All patients achieved remission, with decreases observed in creatinine, proteinuria, CRP, ANCA level and BVAS. Three patients requiring dialysis at presentation became dialysis independent. Two patients required the introduction of maintenance GC for treatment of vasculitis. Overall outcomes were comparable to those of two matched cohorts (n = 172) from previous European Vasculitis Society (EUVAS) trials, but with lower total exposure to CYC and GCs (P < 0.001) and reduced rates of severe infections (P = 0.02) compared with the RITUXVAS (rituximab versus cyclophosphamide in AAV) trial. We found no new cases of diabetes in the first year compared with historic rates of 8.2% from the EUVAS trials (P = 0.04).

Conclusion

Early GC withdrawal in severe AAV is as effective for remission induction as the standard of care and is associated with reduced GC-related adverse events.

IgG4-related disease in a multi-ethnic community: clinical characteristics and association with malignancy

BACKGROUND

Immunoglobulin-G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory condition that can affect multiple organs. Despite growing interest in this condition, the natural history and management of IgG4-RD remain poorly understood.

AIM

To describe the clinical characteristics, treatment and outcomes of IgG4-RD in a multi-ethnic UK cohort, and investigate its possible association with malignancy.

DESIGN

Retrospective analysis of case-note and electronic data.

METHODS

Cases were identified from sub-specialty cohorts and a systematic search of an NHS trust histopathology database using 'IgG4' or 'inflammatory pseudotumour' as search terms. Electronic records, imaging and histopathology reports were reviewed.

RESULTS

In total, 66 identified cases of IgG4-RD showed a similar multi-ethnic spread to the local population of North West London. The median age was 59 years and 71% of patients were male. Presenting symptoms relating to mass effect of a lesion were present in 48% of cases and the mean number of organs involved was 2.4. Total of 10 patients had reported malignancies with 6 of these being haematological. 83% of those treated with steroids had good initial response; however, 50% had relapsing-remitting disease. Rituximab was administered in 11 cases and all achieved an initial serological response. Despite this, seven patients subsequently relapsed after a mean duration of 11 months and four progressed despite treatment.

CONCLUSIONS

We report a large UK-based cohort of IgG4-RD that shows no clear ethnic predisposition and a wide range of affected organs. We discuss the use of serum IgG4 concentrations as a disease marker in IgG4-RD, the association with malignant disease and outcomes according to differing treatment regimens.

Mycophenolate mofetil and tacrolimus versus tacrolimus alone for the treatment of idiopathic membranous glomerulonephritis: a randomised controlled trial

Background

Tacrolimus (TAC) is effective in treating membranous nephropathy (MN); however relapses are frequent after treatment cessation. We conducted a randomised controlled trial to examine whether the addition of mycophenolate mofetil (MMF) to TAC would reduce relapse rate.

Methods

Forty patients with biopsy proven idiopathic MN and nephrotic syndrome were randomly assigned to receive either TAC monotherapy (n = 20) or TAC combined with MMF (n = 20) for 12 months. When patients had been in remission for 1 year on treatment the MMF was stopped and the TAC gradually withdrawn in both groups over 6 months. Patients also received supportive treatment with angiotensin blockade, statins, diuretics and anticoagulation as needed. Primary endpoint was relapse rate following treatment withdrawal. Secondary outcomes were remission rate, time to remission and change in renal function.

Results

16/20 (80%) of patients in the TAC group achieved remission compared to 19/20 (95%) in the TAC/MMF group (p = 0.34). The median time to remission in the TAC group was 54 weeks compared to 40 weeks in the TAC/MMF group (p = 0.46). There was no difference in the relapse rate between the groups: 8/16 (50%) patients in the TAC group relapsed compared to 8/19 (42%) in the TAC/MMF group (p = 0.7). The addition of MMF to TAC did not adversely affect the safety of the treatment.

Conclusions

Addition of MMF to TAC does not alter the relapse rate of nephrotic syndrome in patients with MN.

Trial registration

This trial is registered with EudraCTN2008–001009-41. Trial registration date 2008-10-08.

Renal effects of novel antiretroviral drugs

Chronic kidney disease (CKD) is a critical comorbidity for patients living with HIV, with an estimated prevalence between 2.4 and 17%. Such patients are increasingly affected by diseases associated with ageing, including cardiovascular disease and CKD, and the prevalence of risk factors such as smoking and dyslipidaemia is increased in this population. Proteinuria is also now recognized as a common finding in individuals living with HIV. While combination antiretroviral (ARV) treatments reduce CKD in the HIV-infected population overall, some ARV drugs have been shown to be nephrotoxic and associated with worsening renal function. Over the last few years, several highly efficacious new ARV agents have been introduced. This brief review will look at the novel agents dolutegravir, raltegravir, elvitegravir, cobicistat, tenofovir alafenamide fumarate and atazanavir, all of which have been licensed relatively recently, and describe issues relevant to renal function, creatinine handling and potential nephrotoxicity. Given the prevalence of CKD, the wide range of possible interactions between HIV, ARV therapy, CKD and its treatments, nephrologists need to be aware of these newer agents and their possible effect on kidneys.

Treatment-limiting renal tubulopathy in patients treated with tenofovir disoproxil fumarate

OBJECTIVES

Tenofovir disoproxil fumarate (TDF) is widely used in the treatment or prevention of HIV and hepatitis B infection. TDF may cause renal tubulopathy in a small proportion of recipients. We aimed to study the risk factors for developing severe renal tubulopathy.

METHODS

We conducted an observational cohort study with retrospective identification of cases of treatment-limiting tubulopathy during TDF exposure. We used multivariate Poisson regression analysis to identify risk factors for tubulopathy, and mixed effects models to analyse adjusted estimated glomerular filtration rate (eGFR) slopes.

RESULTS

Between October 2002 and June 2013, 60 (0.4%) of 15,983 patients who had received TDF developed tubulopathy after a median exposure of 44.1 (IQR 20.4, 64.4) months. Tubulopathy cases were predominantly male (92%), of white ethnicity (93%), and exposed to antiretroviral regimens that contained boosted protease inhibitors (PI, 90%). In multivariate analysis, age, ethnicity, CD4 cell count and use of didanosine or PI were significantly associated with tubulopathy. Tubulopathy cases experienced significantly greater eGFR decline while receiving TDF than the comparator group (-6.60 [-7.70, -5.50] vs. -0.34 [-0.43, -0.26] mL/min/1.73 m²/year, p < 0.0001).

CONCLUSIONS

Older age, white ethnicity, immunodeficiency and co-administration of ddI and PI were risk factors for tubulopathy in patients who received TDF-containing antiretroviral therapy. The presence of rapid eGFR decline identified TDF recipients at increased risk of tubulopathy.

Necrotizing and crescentic glomerulonephritis presenting with preserved renal function in patients with underlying multisystem autoimmune disease: a retrospective case series

Objective. Necrotizing and crescentic GN usually presents with rapidly declining renal function, often in association with multisystem autoimmune disease, with a poor outcome if left untreated. We aimed to describe the features of patients who have presented with these histopathological findings but minimal disturbance of renal function.

Methods. We conducted a retrospective review (1995–2011) of all adult patients with native renal biopsy–proven necrotizing or crescentic GN and normal serum creatinine (<120 μmol/l) at our centre.

Results. Thirty-eight patients were identified. The median creatinine at presentation was 84 μmol/l and the median proportion of glomeruli affected by necrosis or crescents was 32%. Clinicopathological diagnoses were ANCA-associated GN (74%), LN (18%), anti-GBM disease (5%) and HScP (3%). Only 18% of cases had pre-existing diagnoses of underlying multisystem autoimmune disease, although the majority (89%) had extra-renal manifestations accompanying the renal diagnosis. All patients received immunosuppression and most had good long-term renal outcomes (median duration of follow-up 50 months), although two progressed to end-stage renal disease within 3 years. We estimate that renal biopsy had an important influence on treatment decisions in 82% of cases.

Conclusion. Necrotizing and crescentic GN may present in patients with no or only minor disturbance of renal function. This often occurs in patients with underlying systemic autoimmune disease; early referral for biopsy may affect management and improve long-term outcomes in these cases.

Long-term outcome of anti-neutrophil cytoplasm antibody-associated glomerulonephritis: evaluation of the international histological classification and other prognostic factors

BACKGROUND

Anti-neutrophil cytoplasm antibody (ANCA) associated vasculitis with renal involvement requires treatment with potentially toxic drugs to reduce morbidity and mortality, and there is a major challenge to determine clinical and histological features predictive of renal prognosis. The aim of our study was to evaluate the use of the 2010 international histological classification for ANCA-associated glomerulonephritis (AAGN) as a predictor of renal outcome when used in conjunction with other prognostic factors.

METHODS

One hundred and four patients with AAGN treated at our centre were included: 23 were classified as focal, 26 as crescentic, 48 as mixed and 7 as sclerotic. Renal outcomes were based on estimated glomerular filtration rate (eGFR) at 1 and 5 years, and on renal survival.

RESULTS

By univariate analysis, patients in the focal class had the best renal outcome, those in the sclerotic class the worst outcome, and those in the mixed and crescentic classes had intermediate renal survival. There was no significant difference in outcome between the mixed and crescentic classes. In multivariate models, histological class did not improve model fit or associate with renal outcome after adjusting for established prognostic factors. Lower percentage of normal glomeruli, greater degree of tubular atrophy (TA), MPO-ANCA positivity, increasing age and lower starting eGFR, all correlated with poorer renal outcomes.

CONCLUSIONS

We conclude that, in our cohort of patients, the international histological classification is predictive of renal outcome in AAGN, but did not appear to be additionally informative over other established prognostic factors in multivariate analysis. However, it may be of value to combine the current histological classification with other established parameters, such as TA and percentage normal glomeruli.

Kidney transplantation in HIV-positive adults: the UK experience

HIV-positive patients are at increased risk of end-stage kidney disease (ESKD). Kidney transplantation (KT) is an established treatment modality for ESKD in the general population. Recent data have confirmed the feasibility of kidney transplantation in HIV-positive patients, and kidney transplantation is increasingly offered to ESKD patients with well-controlled HIV infection. We report clinical outcomes in a national cohort study of kidney transplantation in HIV-positive patients. In all, 35 HIV-positive KT recipients who had undergone KT up to December 2010 (66% male, 74% black ethnicity) were identified; the median CD4 cell count was 366, all had undetectable HIV RNA levels at kidney transplantation, and 44% received a kidney from a live donor. Patient survival at 1 and 3 years was 91.3%, and graft survival 91.3% and 84.7%, respectively. At one-year post-kidney transplantation, the cumulative incidence of acute rejection was 48%, and the median (IQR) eGFR was 64 (46, 78) mL/min/1.73 m(2). Although HIV viraemia and HIV disease progression were uncommon, renal complications were relatively frequent. Our study corroborates the feasibility of kidney transplantation in HIV-positive patients. The high rates of acute rejection suggest that the optimal immune suppression strategy in this population remains to be refined.

Clinical outcomes of a combined HIV and renal clinic

Background

Renal disease is an emerging problem in patients living with human immunodeficiency virus (HIV), as illustrated by an increased incidence of acute kidney injury and chronic kidney disease (CKD) from HIV, its associated treatment and comorbidities such as diabetes and vascular disease. We have established a combined HIV-renal clinic to manage such patients, enhance their treatment and minimize outpatient visits.

Methods

We have analysed the outcomes of the first 99 patients seen in the clinic using electronic patient records. These ninety-nine patients were referred to the service from HIV physicians in West London and all the patients were seen jointly by an HIV and a renal consultant.

Results

Sixty-five percent of the patients were referred with reduced renal function or proteinuria [mean creatinine at presentation 136 mcmol/L, estimated glomerular filtration rate (eGFR) 57 mL/min/1.73 m²]. The majority (53%) had risk factors predisposing to vascular disease including diabetes, hypertension, previous stroke or myocardial infarction. Overall, 27% of patients had a renal diagnosis directly associated with HIV (HIVAN, immune complex nephritis, tenofovir toxicity, Fanconi syndrome), 73% had an alternative possible cause. Twenty-seven percent of patients had low-level proteinuria (urine protein:creatinine ratio abnormal but <100 mg/mmol) or mildly reduced eGFR (40–66 mL/min/1.73 m²) without a clear underlying cause. Ten percent of patients were thought to have tenofovir-induced renal damage all of whom improved on cessation of this agent. Following the review in the combined clinic, 64% of patients had a change in treatment or management, with 50% improving their renal parameters as a result. Most patients were discharged back to their main HIV teams for ongoing follow-up.

Conclusions

A combined HIV-renal clinic can enhance patient care with reduced outpatient visits.

Plasmapheresis in immunologic renal disease

Plasmapheresis has been used in the management of immunologic renal disease for the last 40 years. The rationale behind this approach is to remove pathogenic immune mediators, such as autoantibodies and immune complexes, from the circulation. There may also be benefit in depleting proinflammatory molecules, such as complement components and coagulation factors. Initial experience was gained in Goodpasture's disease, in which antiglomerular basement membrane antibodies were known to be pathogenic. More recently, a role for autoantibodies has become clear in small-vessel systemic vasculitis and some cases of hemolytic uremic syndrome/thrombotic thrombocytopenic purpura. Removal of immune complexes is thought to be important in cryoglobulinemia and systemic lupus erythematosus. Plasmapheresis is used in renal transplantation for the treatment of acute antibody-mediated rejection, and for desensitization of patients with preformed anti-HLA antibodies or those receiving an ABO-incompatible transplant. Although many of the early studies were uncontrolled, there has been an increasing number of randomized controlled trials in recent years. The aim of this article is to summarize current indications for the use of plasmapheresis in immunologic renal disease.

An atypical cutaneous presentation of vasculitis with features of Churg-Strauss syndrome, associated with anti-neutrophil cytoplasmic antibodies and anti-glomerular basement membrane antibodies

We report the case of a 59-year-old woman who presented with a persistent papular and nodular cutaneous eruption and new-onset asthma, with normal renal function but persistent haematuria and proteinuria. Investigations revealed eosinophilia, both antineutrophil cytoplasmic antibodies and antiglomerular basement membrane antibodies on serological testing (double-positive vasculitis), and a focal necrotizing glomerulonephritis on renal biopsy. Histological examination of a skin biopsy showed a dense neutrophilic infiltrate with focal fibrinoid necrosis and few eosinophils. The clinical and pathological features suggested a double-positive vasculitis/Churg-Strauss overlap syndrome presenting with a predominantly neutrophilic dermatosis. Specific cutaneous features in patients with double-positive vasculitis have not been documented previously. The patient has responded extremely well to immunosuppressive treatment and her disease is currently in remission.

Metformin: effective and safe in renal disease?

There is good evidence supporting more extensive use of metformin in type 2 diabetes, in reducing morbidity and mortality. The evidence for a real problem from metformin-induced lactic acidosis is weak, and the risks of alternative agents are often overlooked. We have examined the available data regarding metformin that might cause concern in patients with kidney disease, and find it to be extremely limited. There is no good data on which to offer guidance, but it seems likely that metformin can be used in patients with GFR 60-90 ml/min but at reduced dose at lower levels of GFR, and can probably be safely used at GFRs from 30-60 ml/min but with the same caution as with any renally excreted drug. The risks (often overlooked) and benefits of alternative hypoglycaemic agents should be considered carefully. The overall evidence that metformin causes major harm is poor.

Is there a role for intensive insulin therapy in patients with kidney disease?

There is increasing evidence for the benefit of intensive insulin therapy in maintaining near-normoglycemia in patients without diabetes with severe acute illness. Morbidity and mortality have both improved, with decreased episodes of sepsis, acute kidney injury, transfusion requirements, and post-intensive care complications. The metabolic mayhem of severe acute illness has many parallels with those induced by kidney failure itself, and patients with kidney failure are at increased risk from many of the complications potentially improved by insulin therapy. We reviewed the potential benefits of intensive insulin therapy and examined the published trials for data directly applicable to patients with kidney failure. There are no trials directly answering the question and no specific analysis of patients with kidney disease in published studies. We extracted pertinent data regarding patients with impaired renal function from the reported trials, identified parallels between patients with kidney injury and other severe illnesses, and suggest possible future studies. We hypothesize that intensive insulin therapy has a role outside the intensive care setting and, in particular, a role for patients with severe acute illness and kidney failure, whether acute or chronic.

Impact of new dialysis solutions on peritonitis rates

Peritonitis remains a major cause of morbidity among patients on peritoneal dialysis (PD), yet there is little information about the effect of new biocompatible dialysis solutions on peritonitis rates and treatment. In our unit, information on each peritonitis episode is prospectively collected. Since 2003, bicarbonate/lactate dialysate has been gradually introduced for new patients and for patients experiencing abdominal pain with conventional lactate solutions. From 2002 to 2005, data from 121 episodes of peritonitis (71 automated PD and 50 continuous ambulatory PD) were analyzed; 107 episodes occurred in patients using standard lactate dialysate and 14 episodes in patients using bicarbonate/lactate solution. Patients using bicarbonate/lactate had a significantly lower peritonitis rate of 1 per 52.5 patient-months compared to those using standard lactate dialysate (1 per 26.9 patient-months) (P=0.0179). Response to treatment, however, was not affected by the type of dialysate; cure rates (71.4 and 69.1%, respectively) and recurrence rates (21.4 and 15.8%, respectively) were not significantly different. Catheter removal was required in three (21.4%) patients using bicarbonate/lactate and 23 (22.4%) patients using lactate solution. Use of biocompatible dialysate appears to reduce the peritonitis rate by 50%, although this has to be confirmed in a randomized study. The type of dialysate, on the other hand, does not affect response to treatment.

Fluorodeoxyglucose positron emission tomography detects the inflammatory phase of sclerosing peritonitis

OBJECTIVE

We studied the effectiveness of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in detecting inflammation in known or suspected cases of sclerosing peritonitis in patients on peritoneal dialysis (PD).

DESIGN

We undertook FDG-PET scanning in PD patients presenting with symptoms or signs suggestive of sclerosing peritonitis (SP), and in patients on long-term PD with no symptoms of SP.

SETTING

The study was performed in a PD unit in a tertiary-care hospital.

PATIENTS AND METHODS

Three patients with known or strongly suspected SP underwent FDG-PET scans, 1 within 3 months of presentation with symptoms and 2 who were scanned more than 9 months after presentation. One patient was scanned at an early and a late time point. Five patients who had been on PD for more than 5 years and who were asymptomatic also underwent FDG-PET scanning. Scans were interpreted by a specialist in nuclear medicine.

RESULTS

The scan performed in the early stages of SP showed increased peritoneal uptake. However, three scans taken more than 9 months after presentation with suspected SP showed mild peritoneal abnormalities only. One of 5 asymptomatic long-term PD patients showed increased peritoneal uptake associated with loss of ultrafiltration and high transporter status.

CONCLUSIONS

FDG-PET scanning may be a useful adjunct in the diagnosis of the acute phase of SP. More study is needed to define its role in the diagnosis of SP in asymptomatic PD patients.

Clinical features and outcome of patients with both ANCA and anti-GBM antibodies

BACKGROUND

Patients have been described who have both anti-neutrophil cytoplasm antibodies (ANCA) and anti-glomerular basement membrane (GBM) antibodies. We have attempted to define the true prevalence of such "double positive" patients, and describe in detail their clinical features and outcome.

METHODS

We have reviewed all serologic assays performed between 1990 and 2000 in a single institution, and the case notes of patients having sera positive for both ANCA and anti-GBM antibodies. During this time 20,392 sera were initially tested for ANCA, and 4808 sera tested for anti-GBM antibodies.

RESULTS

Five percent of all ANCA-positive serum samples were also positive for anti-GBM antibodies, and 32% of all anti-GBM positive samples had detectable ANCA. Of 27 patients with both antibodies, 82% had anti-myeloperoxidase specific P-ANCA. Pulmonary hemorrhage occurred in 44%. Renal biopsy showed extensive glomerular cellular crescents in most patients. Patient and renal survival rates were 52% and 26%, respectively, at one year. Sixty-eight percent of patients were dialysis-dependent at presentation, and none of these recovered renal function, despite immunosuppression with or without plasma exchange.

CONCLUSION

Serologic evidence of double positivity for both ANCA and anti-GBM antibodies is common in patients with either antibody. In our study these patients have a poor prognosis when presenting with severe disease and initially behave more like anti-GBM disease than vasculitis. Recovery from severe renal failure is rare.

Urinary monocyte chemoattractant protein-1 (MCP-1) is a marker of active renal vasculitis

BACKGROUND

Macrophage infiltration and cytokine production are important in the pathogenesis of crescentic glomerulonephritis in anti-neutrophil cytoplasm antibody (ANCA)-associated vasculitis. The aim of this study was to investigate whether urinary levels of chemokines, monocyte chemoattractant protein-1 (MCP-1) and fractalkine, were useful tools for non-invasive assessment of renal vasculitis.

METHODS

In a prospective study, concentrations of chemokines were measured in urine and serum samples using specific enzyme-linked immunosorbent assays, and related to the patients' clinical status. Renal expression of MCP-1 was studied by immunohistochemical staining of renal biopsies.

RESULTS

Urinary levels of MCP-1 were significantly higher in patients with active (P<0.01) or persistent (P<0.05) renal vasculitis, in comparison with healthy volunteers, control patients, patients with inactive vasculitis and patients with extra-renal disease only. There were no differences in serum concentrations of MCP-1 between these groups. Reduction in urinary MCP-1 levels following treatment preceded the improvement of renal function by a median of 2 weeks. In one patient, rising urinary levels of MCP-1, despite immunosuppressive therapy, was associated with progression to severe renal failure. There were no differences in urinary fractalkine levels between the different groups of patients and controls. Immunohistology of renal biopsies from patients with crescentic glomerulonephritis showed increased staining for MCP-1 in glomerular and interstitial cells. Urinary MCP-1 levels correlated with glomerular, but not tubulointerstitial, macrophage infiltration (P<0.05).

CONCLUSIONS

This study shows that measurement of urinary MCP-1, but not fractalkine, is a useful non-invasive technique for the assessment of renal involvement and monitoring the response to therapy in ANCA-associated vasculitis.

Characterization of autoantibodies from patients with Goodpasture's disease using a resonant mirror biosensor

Goodpasture's disease is characterized by the binding of IgG autoantibodies to the glomerular basement membrane, leading to glomerular inflammation. The autoantigen has been identified as the noncollagenous domain of the alpha3 chain of type IV collagen (alpha3(IV)NC1). We have used the IAsys resonant mirror biosensor to analyse the extent and affinity of binding of anti-GBM antibodies from sera of patients to purified alpha3(IV) NC1. alpha3(IV) NC1 monomers were immobilized to a carboxylate cuvette, with the simultaneous use of a control well. The binding of serum from patients with Goodpasture's disease (n = 12), normal controls (n = 14) and disease controls with vasculitis (n = 14) was analysed. Antibody binding was detected in sera from all patients with Goodpasture's disease but not from controls. IAsys measurements of binding correlated with antibody levels assessed by the standardized ELISA used for clinical assays. Both ELISA and biosensor measurements showed declining antibody levels in serial serum samples from treated patients; however, the biosensor detected antibody recrudescence when ELISA remained negative. Autoantibodies from patients' serum had average affinity constants (Kd) of 6.5 x 10-11M to 52.07 x 10-10M, as determined by an inhibition assay, indicating high affinity. Sips analysis showed that the antibody response was relatively homogeneous (values of 0.46-1). Biosensor techniques can therefore be used to detect and characterize anti-GBM antibodies in serum from patients, with high sensitivity and without need for antibody purification. This technique may be useful in diagnosis and monitoring of patients with Goodpasture's disease, and may be applicable to other autoantibody mediated diseases.

Goodpasture's disease in the absence of circulating anti-glomerular basement membrane antibodies as detected by standard techniques

Goodpasture's disease is characterized by rapidly progressive glomerulonephritis, often accompanied by pulmonary hemorrhage, in association with deposition of antibodies in a linear pattern on the glomerular basement membrane (GBM). The diagnosis of Goodpasture's disease in patients with acute renal failure often relies on the use of immunoassays to detect circulating anti-GBM antibodies in serum samples. We describe three cases of Goodpasture's disease in which no circulating anti-GBM antibodies were detectable in serum by well-established enzyme-linked immunosorbent assay or Western blotting techniques. The diagnosis of Goodpasture's disease was confirmed by renal biopsy, with linear deposition of immunoglobulin along the GBM and crescentic glomerulonephritis. In addition, an alternative method of antibody detection using a highly sensitive biosensor system confirmed that circulating antibodies were present in sera from both patients tested. Because this technique is not routinely available for the detection of anti-GBM antibodies, we suggest that diagnosis always be confirmed with a renal biopsy, and despite negative serological test results using immunoassay, the diagnosis of Goodpasture's disease should still be considered in the correct clinical context.

In Goodpasture's disease, CD4(+) T cells escape thymic deletion and are reactive with the autoantigen alpha3(IV)NC1

Goodpasture's disease is characterized by rapidly progressive glomerulonephritis and pulmonary hemorrhage, in association with circulating and deposited anti-glomerular basement membrane antibodies that recognize the alpha3 chain of type IV collagen [alpha3(IV)NC1] (known as the Goodpasture antigen). Unlike many other autoimmune diseases, recurrences are rare. In experimental models and human studies, both humoral and cellular mechanisms have been demonstrated to be involved in disease pathogenesis. However, there are few data on the characteristics of the autoreactive T cells or the mechanisms of tolerance to the autoantigen in human patients. It was demonstrated, using immunohistochemical analyses and reverse transcription-PCR, that the Goodpasture antigen is expressed in normal human thymus. Using limiting dilution analyses, the frequencies of circulating autoreactive T cells in patients and control subjects were assessed. During acute disease, there were increased frequencies of CD4(+) T cells reactive with alpha3(IV)NC1 (ranging from 1:6300 to 1:65,000), which decreased with time. There was a significant difference between patients during their acute disease phase and control subjects with respect to the frequency index for alpha3(IV)NC1-specific CD4(+) T cells (P < 0.05, Mann Whitney U test). The decrease in autoreactive CD4(+) T-cell numbers during recovery may be the reason why recurrences are infrequent and may explain the loss of pathogenic autoantibodies with time, because of a lack of T-cell help.

Long-term outcome of anti-glomerular basement membrane antibody disease treated with plasma exchange and immunosuppression

BACKGROUND

Anti-glomerular basement membrane (GBM) antibody disease is an autoantibody-mediated disorder that usually presents as rapidly progressive glomerulonephritis, often with pulmonary hemorrhage (the Goodpasture syndrome). It is reported that patients with severe renal failure do not generally recover renal function.

OBJECTIVE

To examine the long-term outcome of severe anti-GBM antibody disease.

DESIGN

Retrospective review of patients treated for confirmed anti-GBM antibody disease over 25 years.

SETTING

A tertiary referral center in the United Kingdom.

PATIENTS

71 treated patients with anti-GBM antibody disease.

INTERVENTION

All patients received plasma exchange, prednisolone, and cyclophosphamide.

MEASUREMENTS

Patient and renal survival, renal histology, and antibody levels.

RESULTS

Patients who presented with a creatinine concentration less than 500 micromol/L (5.7 mg/dL) (n = 19) had 100% patient survival and 95% renal survival at 1 year and 84% patient survival and 74% renal survival at last follow-up. In patients who presented with a creatinine concentration of 500 micromol/L or more (>/=5.7 mg/dL) (n = 13) but did not require immediate dialysis, patient and renal survival were 83% and 82% at 1 year and 62% and 69% at last follow-up. In patients who presented with dialysis-dependent renal failure (n = 39), patient and renal survival were 65% and 8% at 1 year and 36% and 5% at last follow-up. All patients who required immediate dialysis and had 100% crescents on renal biopsy remained dialysis dependent.

CONCLUSIONS

Patients with the Goodpasture syndrome and severe renal failure should be considered for urgent immunosuppression therapy, including plasma exchange, to maximize the chance of renal recovery. Patients needing immediate dialysis are less likely to recover.

Nephrotoxicity of intravenous immunoglobulin

Individual case reports have documented nephrotoxicity of intravenous immunoglobulin (IVIG) preparations, but the true incidence of renal dysfunction is unknown and many data sheets do not include renal impairment as a side-effect of these preparations. We determined the incidence of renal impairment in an unselected cohort of patients receiving two different preparations of IVIG over 20 months, administering 287 courses of IVIG to 119 patients for a variety of indications, including thrombocytopenia, systemic lupus erythematosis, neuropathy, Guillain-Barre syndrome and infections. Two different preparations of IVIG were used, Vigam (BPL) and Sandoglobulin (Novartis), which differ in the concentration of sucrose added as a stabilizer. Eight patients showed deterioration in renal function (6.7%), and in two, no renal recovery occurred (1. 7%). There were no significant differences in the patient characteristics or dose or preparation of IVIG administered to those patients with or without changes in serum creatinine. There was no association between the amount of sucrose in the IVIG and development of renal failure. IVIG (regardless of the sucrose content) is associated with renal impairment which may be irreversible, with a maximum incidence of 6.7%. All patients should have their renal function monitored during the use of IVIG.

The tyrosine phosphatase SHP-1 is a negative regulator of osteoclastogenesis and osteoclast resorbing activity: increased resorption and osteopenia in me(v)/me(v) mutant mice

Naturally occuring inactivating mutations of the Src homology 2 (SH2) domain-containing tyrosine phosphatase 1 (SHP-1) in mice give rise to the motheaten (me) phenotype. me/me mice have multiple hematopoietic abnormalities, suggesting that this phosphatase plays an important role in hematopoiesis. SHP-1 binds to and is activated by several hematopoietic surface receptors, including the colony-stimulating factor type 1 receptor. We have examined the role of SHP-1 in osteoclastogenesis and osteoclast function using mice with the viable motheaten (me(v)/me(v)) mutation, which has markedly decreased SHP-1 activity. Histomorphometric analysis of 6-week-old me(v)/me(v) mice and control littermates showed a marked osteopenia with an increase in bone resorption indices. The number of formed osteoclast-like cells (OCLs) in cocultures of me(v)/me(v) hematopoietic cells with normal osteoblasts was significantly increased. In contrast, the number of OCLs formed in the coculture of normal bone marrow cells with the me(v)/me(v) osteoblasts was not significantly different from controls. The bone-resorbing activity of me(v)me(v) OCLs and authentic osteoclasts was also found to be increased. Finally, Western blotting of proteins from me(v)/me(v) and control OCLs revealed an overall increase in tyrosine phosphorylation in the me(v)/me(v) lysates. These in vivo and in vitro results suggest that SHP-1 is a negative regulator of bone resorption, affecting both the formation and the function of osteoclasts.

Urological complications after kidney-pancreas transplantation

PURPOSE

Urological complications are common after kidney-pancreas transplantation. Predictors of urological complication after transplantation have not been established. We studied the impact of urological complications on allograft function. In addition we evaluated age at transplantation, diabetic years before transplantation and preoperative bladder function as predictors of allograft pancreatitis, postoperative retention and urine leaks.

MATERIALS AND METHODS

Urological complications in 65 cases (38 men, 27 women, mean diabetic years 21 +/- 6, mean age 33 +/- 7 years) who had transplants between December 1987 and January 1995 were reviewed. Preoperative urodynamics in 50 patients (77%) and voiding cystourethrogram in 40 (62%) were analyzed. Kidney-pancreas transplantation was completed using bladder drainage techniques.

RESULTS

Mean followup was 44 +/- 27 months (median 40, range 1 to 93). Urological complications in 51 patients (79%) included urinary tract infection in 59%, hematuria in 26%, allograft pancreatitis in 19%, duodenal leaks in 17%, ureteral lesions in 9% and urethral lesions in 6%. Eleven duodenal leaks (8 leaks in less than 1 month) required surgical treatment. Nine leaks recurred in 7 patients. Allograft pancreatitis occurred 32 times (range 1 to 9) in 12 patients. Three patients had ureteral obstruction and 3 had ureteral leaks. Preoperative urodynamics included detrusor hyperreflexia in 8 patients, detrusor areflexia in 19, indeterminate in 5 and normal in 18. The 1-year patient, kidney and pancreatic allograft survival rates were 92, 91 and 86%; 2-year survival rates were 89, 88 and 80%, and 5-year survival rates were 61, 59 and 55%, respectively.

CONCLUSIONS

Urological complications were common after transplantation but did not adversely affect allograft survival in our series. Age at transplantation, diabetic years preceding transplantation and preoperative bladder function were not significantly correlated with allograft pancreatitis, postoperative urinary retention or urine leaks. A prospective analysis of postoperative bladder function should be completed to improve understanding and possibly reduce morbidity of urological complications after transplantation.

Colony-stimulating factor-1 induces cytoskeletal reorganization and c-src-dependent tyrosine phosphorylation of selected cellular proteins in rodent osteoclasts

Colony-stimulating factor-1 (CSF-1) stimulates motility and cytoplasmic spreading in mature osteoclasts. Therefore, we examined the cellular events and intracellular signaling pathways that accompany CSF-1-induced spreading in normal osteoclasts. To explore the role c-src plays in these processes, we also studied osteoclasts prepared from animals with targeted disruption of the src gene. In normal osteoclasts, CSF-1 treatment induces rapid cytoplasmic spreading, with redistribution of F-actin from a well-delineated central attachment ring to the periphery of the cell. CSF-1 increases membrane phosphotyrosine staining in osteoclasts and induces the phosphorylation of several cellular proteins in cultured, osteoclast-like cells, including c-fms, c-src, and an 85-kD Grb2-binding protein. Src kinase activity is increased threefold after CSF-1 treatment. In src- cells, no attachment ring is present, and CSF-1 fails to induce spreading or a change in the pattern of F-actin distribution. Although c-fms becomes phosphorylated after CSF-1 treatment, the 85-kD protein is significantly less phosphorylated in src- osteoclast-like cells. These results indicate that c-src is critical for the normal cytoskeletal architecture of the osteoclast, and, in its absence, the spreading response induced by CSF-1 is abrogated, and downstream signaling from c-fms is altered.

Mapping B cell epitopes in Goodpasture's disease

The target antigen of the pathogenic autoantibodies in Goodpasture's disease is the noncollagenous domain of the alpha 3 chain of type IV collagen. A panel of membrane-bound peptides was used to identify antibody-binding regions within the protein, and the significance of the binding by inhibition studies using soluble peptides, and by a structural analysis of the antigen, was confirmed. A total of 117 overlapping 12-mer peptides spanning the entire antigen was simultaneously synthesized as individual spots on a cellulose membrane. All nine patients' sera bound to the membrane, with a conserved pattern of peptides recognized by all sera. Inhibition studies were performed using a panel of overlapping 20-mer peptides, also spanning the entire antigen. Peptides from the regions that bound IgG were able to inhibit the binding of autoantibodies to native antigen. Predictions of the secondary structure of the noncollagenous domain of the alpha 3 chain of type IV collagen were performed by a conventional hydropathy plot and by multiple alignment of homologous alpha chains of type IV collagen and comparison with a structural data base. The core peptides binding and inhibiting Goodpasture's antibodies were predicted to be surface exposed and antigenic. Thus, the conformational epitope(s) of the Goodpasture antigen can be mapped using linear peptides.

Modified pudendal-thigh flap for correction of penoscrotal transposition

OBJECTIVES

In patients with penoscrotal transposition, an occasional postoperative problem has been a deficiency of skin on the proximal penile shaft that results in penoscrotal fusion and tethering.

METHODS

We describe a new operation using a modified neurovascular pudendal-thigh flap for correction of incomplete penoscrotal transposition.

RESULTS

This procedure has been used in 6 children, and an excellent cosmetic and functional result has been achieved in each patient.

CONCLUSIONS

The flaps provide a reliable blood supply, maintain normal innervation, and correct the problem of postoperative penoscrotal fusion and tethering. This technique preserves sufficient penile skin for a tension-free second-stage urethroplasty.

Hypertension after surgical management of renal duplication associated with an upper pole ureterocele

PURPOSE

Duplicated upper pole systems associated with a ureterocele frequently have areas of segmental renal dysplasia. Since dysplasia has been related to the development of renin mediated hypertension, we hypothesized that preservation of functional upper pole moieties may result in an increased incidence of high blood pressure.

MATERIALS AND METHODS

We evaluated 115 patients with a history of renal duplication and an ipsilateral upper pole ureterocele. Patients were separated into group 1-nonfunctional upper pole managed by partial nephrectomy, group 2-functional upper pole moiety managed by partial nephrectomy and group 3-functional upper pole moiety managed by a nephron sparing procedure. All charts were reviewed for hypertension, febrile urinary tract infection, vesicoureteral reflux and renal scarring.

RESULTS

At a median followup age of 15 years (range 1 to 33) hypertension developed in 13 of the 115 patients (11%), including 8 of the 87 (9%) with nonfunctional upper pole systems managed by partial nephrectomy, 1 of the 12 (8%) with a functional upper pole moiety managed by partial nephrectomy and 4 of the 16 (25%) with a functional upper pole system managed by an upper pole salvage procedure. Statistical evaluations failed to reveal any relationship between hypertension and preservation of the upper pole system or between hypertension and vesicoureteral reflux. Rather, elevation in blood pressure was found to be related to development of a renal scar after a febrile urinary tract infection.

CONCLUSIONS

Hypertension in patients with a history of renal duplication associated with a ureterocele is directly related to renal scarring.

Genitourinary neurofibromatosis mimicking posterior urethral valves

A 12-year-old boy, examined after an episode of acute urinary retention, was found to have neurofibromatosis of the bladder neck and prostatic urethra. His symptoms of bladder outlet obstruction and radiographic findings of a dilated prostatic urethra mimicked posterior urethral valves. Complete urologic investigation, including cystourethroscopy, revealed that the dilatation of the prostatic urethra was secondary to neural involvement of the external sphincter and posterior urethra without mechanical obstruction or posterior urethral valves.

Still a role for plasma exchange in rapidly progressive glomerulonephritis?

Plasmapheresis combined with immunosuppression dramatically improved the survival of patients with Goodpasture's disease in the late 1970's. The presence of circulating pathogenic autoantibodies in this disease provided a logical rationale for the use of plasma exchange therapy. Careful analysis of the response to treatment has suggested that patients presenting with a serum creatinine < 600 mumol/I have the most benefit from plasma exchange. Subsequently plasmapheresis has been tried in a variety of other nephritides, predominantly those causing rapidly progressive glomerulonephritis, with variable success. Initial studies failed adequately to distinguish patients with a number of quite distinct causes of crescentic nephritis. However it has become clear that plasma exchange significantly improves the outcome of patients with pauci-immune crescentic glomerulonephritis who present with severe renal failure requiring dialysis, but not those with less severe renal disease.

Identification of a novel 135-kDa Grb2-binding protein in osteoclasts

The tyrosine kinase receptor for macrophage colony-stimulating factor and the non-receptor tyrosine kinase c-Src play critical roles in osteoclast differentiation and function. Since the ubiquitously expressed adaptor protein Grb2 plays an important role in several tyrosine kinase signal transduction pathways, we used a filter binding assay to identify osteoclast proteins that bind to Grb2. In osteoclasts, there were three major Grb2-binding proteins, two of which, mSos and c-Cbl (p120), have been previously identified as Grb2-binding proteins in many cell types. The third protein, p135, had a restricted pattern of expression and was present at high levels in authentic osteoclasts and osteoclast-like cells formed in an in vitro co-culture system. In addition to binding Grb2 in the filter binding assay, p135 was isolated in complexes with endogenous Grb2 from osteoclast cell extracts. The association of p135 and Grb2 was dependent on an intact Src homology 3 domain and furthermore, was shown to preferentially interact with the N-terminal Src homology 3 domain of Grb2, which is similar to the interaction of mSos and Grb2 in other cell types. p135 was not recognized by antibodies against several known Grb2-binding proteins and thus may be a novel Grb2-binding protein.

c-Cbl is downstream of c-Src in a signalling pathway necessary for bone resorption

The primary defect in mice lacking the c-src gene is osteopetrosis, a deficiency in bone resorption by osteoclasts. Osteoclasts express high levels of the c-Src protein and the defect responsible for the osteopetrotic phenotype of the c-src-deficient (src-) mouse is cell-autonomous and occurs in mature osteoclasts. However, the specific signalling pathways that require c-Src expression for normal osteoclast activity have not been elucidated. We report here that the proto-oncogene product c-Cbl is tyrosine-phosphorylated in a Src-dependent manner in osteoclasts, where the two proteins colocalize on some vesicular structures. In vitro bone resorption by osteoclast-like cells (OCLs) is inhibited by both c-src and c-cbl antisense oligonucleotides. Furthermore, tyrosine phosphorylation of c-Cbl and the localization of c-Cbl-containing structures to the peripheral cytoskeleton are impaired in resorption-deficient c-src- OCLs, as well as in wild-type OCLs that have been treated with c-src antisense oligonucleotides. These results indicate that c-Cbl may act downstream of c-Src in a signalling pathway that is required for bone resorption.

Epitope analysis of the Goodpasture antigen using a resonant mirror biosensor

We have used a new technique for studying molecular interactions-a resonant mirror biosensor-to identify B cell epitopes within the Goodpasture antigen, which has recently been identified as the non-collagenous domain of the alpha 3-chain of type IV collagen (alpha 3(IV)NC1). Recombinant antigen (r-alpha 3) was immobilized onto the sensing surface of a sample cuvette, and the binding of patients' autoantibodies or a MoAb to the Goodpasture antigen was followed in real time. All patients' sera bound r-alpha 3 in this system, while control sera did not bind. A MoAb inhibited the binding of all patients' autoantibodies to r-alpha 3, from 27% to 90% (mean inhibition 60%), and patients' sera cross-inhibited the binding of each other to the antigen. Binding was inhibited by pre-incubation of autoantibody with both native sheep alpha 3(IV)NC1 and purified human alpha 3(IV)NC1 monomers. Inhibition experiments using soluble overlapping peptides from human alpha 3(IV)NC1 identified putative B cell epitopes. These results suggest that there is a major immunodominant epitope on the Goodpasture antigen, and that there is very limited heterogeneity in the autoantibody response in Goodpasture's disease. The resonant mirror biosensor can be successfully used to monitor antibody-antigen binding using polyclonal sera, and to map epitopes on autoantigens.

Congenital adrenal hyperplasia: is there an effect on penile growth?

PURPOSE

Experimental evidence in rodents suggests that prepubertal exposure to excess androgens may prematurely down regulate the penile androgen receptor and cause micropenis in adulthood. To evaluate the effect of prepubertal androgens on human penile growth we reviewed phallic development in male patients with congenital adrenal hyperplasia.

MATERIALS AND METHODS

We retrospectively reviewed the records of 12 patients with 21-hydroxylase deficiency. Stretched penile length was recorded at diagnosis and at last followup. Bone age, height and weight were recorded at each visit.

RESULTS

At diagnosis mean z-score for stretched penile length (z-score equals the number of standard deviations above or below the mean, that is z-score for micropenis equals -2.5) was 2.95 (1.23 to 4.88). Final mean z-score for stretched penile length in adulthood was -1.70 (-2.96 to 1.87). Mean decrease in z-score for diagnosis until the last followup was -4.68 (-1.08 to -6.82). Only 2 of the 12 patients (17%) had micropenis in adulthood. Notably excessive adrenal androgen production resulted in diminutive stature with median height in adulthood in the 10th percentile.

CONCLUSIONS

These findings suggest that excessive prepubertal androgen exposure due to congenital adrenal hyperplasia is associated with a reduction in adult somatic height but it does not routinely result in micropenis.

The effects of androgen administration on phallic androgen receptor expression

PURPOSE

Whether androgens down regulate the androgen receptor during penile development is controversial. We investigated the effects of androgens on penile androgen receptor expression.

MATERIALS AND METHODS

We injected prepubertal hypogonadotropic hypogonadal microphallic rats with testosterone or dihydrotestosterone. Specimens were obtained at 3 (prepuberty), 9 (puberty to early postpuberty) and 12 weeks (late postpuberty). At necropsy we compared penile size and androgen receptor expression of these animals to those of age matched nontreated hypogonadotropic hypogonadal and normal controls.

RESULTS

At age 3 weeks prepubertal androgens up regulated androgen receptor expression and significantly increased penile size compared to normal and untreated hypogonadotropic hypogonadal controls. By 9 weeks the normal down regulation of androgen receptor that occurs with maturation was present. Prepubertal androgens failed to accelerate or exaggerate the normal maturational loss of the androgen receptor. At 9 weeks penile size of normal controls and prepubertal androgen treated animals was identical. Interestingly despite down regulation of the penile androgen receptor, normal animals continued to have increases in penile size between 9 and 12 weeks, while the prepubertal androgen treated animals had no penile growth.

CONCLUSIONS

Prepubertal androgen administration in hypogonadotropic hypogonadal animals resulted in diminutive penises in adulthood. However, the decrease in penile size was not associated with an accelerated or exaggerated down regulation of the androgen receptor. This finding coupled with continued growth of the normal control penises after androgen receptor down regulation suggests that cessation of penile growth may not be solely related to down regulation of the penile androgen receptor.