Kidney biopsy findings in children with diabetes mellitus.

BACKGROUND: Diabetic nephropathy may begin in childhood, but clinical kidney disease ascribable to this is uncommon in children with type 1 (insulin dependent) diabetes mellitus. METHODS: We reviewed our experience of kidney biopsies in children with type 1 diabetes mellitus. RESULTS: Between 1995 and 2022, there were biopsies in 17 children, with various clinical indications for kidney biopsy, making this the largest series of biopsies in diabetic children with clinical kidney abnormalities. Four biopsies showed diabetic nephropathy, three showed the combination of diabetic nephropathy and IgA nephropathy, and ten showed a variety of conditions other than diabetic nephropathy: minimal change disease (2), membranous nephropathy (2), thin glomerular basement membrane lesion (2), non-glomerular chronic damage in Wolcott-Rallison syndrome (2), acute pauciimmune necrotizing crescentic glomerulonephritis (1) and IgA nephropathy (1). Clinical clues of something other than diabetic nephropathy included acute kidney injury, microscopic haematuria or chronic kidney impairment with little or no proteinuria and the nephrotic syndrome after a short duration of diabetes. CONCLUSIONS: We confirm that changes better known in adults with either type 1 or type 2 diabetes mellitus can occur in children with type 1 diabetes mellitus: overt diabetic nephropathy either on its own or combined with other conditions and kidney disorders other than diabetic nephropathy.

Long-term outcomes and response to treatment in diacylglycerol kinase epsilon nephropathy.

Recessive mutations in diacylglycerol kinase epsilon (DGKE) display genetic pleiotropy, with pathological features reported as either thrombotic microangiopathy or membranoproliferative glomerulonephritis (MPGN), and clinical features of atypical hemolytic uremic syndrome (aHUS), nephrotic syndrome or both. Pathophysiological mechanisms and optimal management strategies have not yet been defined. In prospective and retrospective studies of aHUS referred to the United Kingdom National aHUS service and prospective studies of MPGN referred to the National Registry of Rare Kidney Diseases for MPGN we defined the incidence of DGKE aHUS as 0.009/million/year and so-called DGKE MPGN as 0.006/million/year, giving a combined incidence of 0.015/million/year. Here, we describe a cohort of sixteen individuals with DGKE nephropathy. One presented with isolated nephrotic syndrome. Analysis of pathological features reveals that DGKE mutations give an MPGN-like appearance to different extents, with but more often without changes in arterioles or arteries. In 15 patients presenting with aHUS, ten had concurrent substantial proteinuria. Identified triggering events were rare but coexistent developmental disorders were seen in six. Nine with aHUS experienced at least one relapse, although in only one did a relapse of aHUS occur after age five years. Persistent proteinuria was seen in the majority of cases. Only two individuals have reached end stage renal disease, 20 years after the initial presentation, and in one, renal transplantation was successfully undertaken without relapse. Six individuals received eculizumab. Relapses on treatment occurred in one individual. In four individuals eculizumab was withdrawn, with one spontaneously resolving aHUS relapse occurring. Thus we suggest that DGKE-mediated aHUS is eculizumab non-responsive and that in individuals who currently receive eculizumab therapy it can be safely withdrawn. This has important patient safety and economic implications.

Genetic studies of focal segmental glomerulosclerosis: a waste of scientific time?

Many genetic causes of focal segmental glomerulosclerosis (FSGS) have been described. A paradox is that the science in the molecular biology, which generally appears of high quality, is not mirrored by a similarly critical analysis of the renal pathology. FSGS has been applied to such a wide range of conditions that it can reasonably be said to have no useful meaning. Attempts to refine the term have been largely ignored. Study of 252 papers on genetic causes of FSGS found various clinical features. Many papers took the reported diagnosis without question. Few papers reported a pathological review, almost half reported FSGS and up to six other conditions caused by any particular gene, some reported FSGS with recognisable glomerular disorders, over 80% did not apply the Columbia classification, and in nearly all with photomicrographs, the images were not useful for refinement of FSGS. Some workers commented on a lack of genotype-phenotype correlation. One reason is a disregard of the principle that scientific investigation requires an unambiguous definition of the condition studied, to allow others to replicate or refute the findings. Genetic studies of FSGS should use a similarly rigorous approach to renal pathology to that used in molecular biology.

Origins of a pervasive, erroneous idea: The "green birefringence" of Congo red-stained amyloid.

Congo red was discovered to stain amyloid by accident in 1922, and Congo red-stained amyloid was shown to be birefringent on polarization microscopy in 1927. Colours, namely green and yellow, were reported under these conditions in 1945, although these are only two of various anomalous colours that may be seen, depending on the optical set-up. In 1953 there began a dogmatic insistence that in Congo red-stained amyloid between crossed polarizer and analyser green alone should be seen, and the finding of any other colour was a mistake. The idea that green, and only green, is essential for the diagnosis of amyloid has persisted almost universally, and virtually all mentions of Congo red-stained amyloid say that it just shows "green birefringence" or "apple-green birefringence." This idea is wrong and is contrary to everyday experience, because green is seldom seen on its own under these conditions of microscopy, and often, there is no green at all. How observers maintain this unscientific position is explained by a study of its historical origins. Most of the early literature was in German or French and was usually quoted in English at second hand, which meant that misquotations, misattributions and misunderstandings were common. Few workers reported their findings accurately, hardly any attempted to explain them, and until 2008, none gave a completely satisfactory account of the physical optics. The history of Congo red-stained amyloid is an instructive example of how an erroneous belief can become widely established even when it is contradicted by simple experience.

Glycine Amidinotransferase (GATM), Renal Fanconi Syndrome, and Kidney Failure.

Background For many patients with kidney failure, the cause and underlying defect remain unknown. Here, we describe a novel mechanism of a genetic order characterized by renal Fanconi syndrome and kidney failure.Methods We clinically and genetically characterized members of five families with autosomal dominant renal Fanconi syndrome and kidney failure. We performed genome-wide linkage analysis, sequencing, and expression studies in kidney biopsy specimens and renal cells along with knockout mouse studies and evaluations of mitochondrial morphology and function. Structural studies examined the effects of recognized mutations.Results The renal disease in these patients resulted from monoallelic mutations in the gene encoding glycine amidinotransferase (GATM), a renal proximal tubular enzyme in the creatine biosynthetic pathway that is otherwise associated with a recessive disorder of creatine deficiency. In silico analysis showed that the particular GATM mutations, identified in 28 members of the five families, create an additional interaction interface within the GATM protein and likely cause the linear aggregation of GATM observed in patient biopsy specimens and cultured proximal tubule cells. GATM aggregates-containing mitochondria were elongated and associated with increased ROS production, activation of the NLRP3 inflammasome, enhanced expression of the profibrotic cytokine IL-18, and increased cell death.Conclusions In this novel genetic disorder, fully penetrant heterozygous missense mutations in GATM trigger intramitochondrial fibrillary deposition of GATM and lead to elongated and abnormal mitochondria. We speculate that this renal proximal tubular mitochondrial pathology initiates a response from the inflammasome, with subsequent development of kidney fibrosis.

Induction treatment of ANCA-associated vasculitis with a single dose of rituximab.

OBJECTIVES: Rituximab is effective in inducing remission in ANCA-associated vasculitis (AAV), with randomized evidence to support its use as four infusions of 375 mg/m(2) (the conventional lymphoma dosing schedule). As B cell depletion (BCD) appears to occur very rapidly after the first dose, we questioned the need for repeat dosing and adopted a standard single-dose protocol of 375 mg/m(2) to treat active AAV. METHODS: All consecutive cases with newly diagnosed or relapsing AAV for whom conventional immunosuppression was contraindicated or ineffective were enrolled. All were rituximab naive. Circulating CD19(+) B cells and clinical and serological markers of disease activity were recorded at regular intervals. Complete remission (CR) was defined as the absence of clinical features of AAV with a prednisolone dose <10 mg/day. RESULTS: Nineteen patients were included, 17 (89%) with generalized disease and 2 (11%) with severe disease (creatinine level >500 µM). Eight (42%) were on additional immunosuppression at the time of rituximab treatment. Satisfactory BCD (<0.005 cells/µl) was achieved in 89% of patients after a median of 13 days. Three-month BCD probability was 89%. Median time to CR following a single dose of rituximab was 38 days and the 3-month probability of CR was 80%. Median time to B cell repopulation was 9.2 months and to disease relapse/redose was 27 months. Use of this single-dose protocol saved an estimated £4533/patient (US$7103; €5276) compared with a 4 × 375 mg/m(2) dosing schedule. CONCLUSION: Our single-centre experience suggests that a single dose of rituximab of 375 mg/m(2) is a reasonable and more cost-effective therapy for inducing remission in patients with AAV.

Early changes in scores of chronic damage on transplant kidney protocol biopsies reflect donor characteristics, but not future graft function.

The amount of irreversible injury on renal allograft biopsy predicts function, but little is known about the early evolution of this damage. In a single-center cohort, we examined the relationship between donor-, recipient-, and transplantation-associated factors and change in a morphometric index of chronic damage (ICD) between protocol biopsies performed at implantation and at 2-3 months. We then investigated whether early delta ICD predicted subsequent biochemical outcomes. We found little evidence to support differences between the study group, who had undergone serial biopsies, and a contemporaneous control group, who had not. In allografts with serial biopsies (n = 162), there was an increase in ICD between implantation (median: 2%, IQR:0-8) and 2-3 months post-transplant (median 8% IQR:4-15; p < 0.0001). Donation from younger or live donors was independently associated with smaller early post-transplant increases in ICD. There was no evidence for a difference in delta ICD between donation after cardiac death vs. donation after brain death, nor association with length of cold ischemia. After adjustment for GFR at the time of the second biopsy, delta ICD after three months did not predict allograft function at one yr. These findings suggest that graft damage develops shortly after transplantation and reflects donor factors, but does not predict future biochemical outcomes.

Acetaminophen inhibits hemoprotein-catalyzed lipid peroxidation and attenuates rhabdomyolysis-induced renal failure.

Hemoproteins, hemoglobin and myoglobin, once released from cells can cause severe oxidative damage as a consequence of heme redox cycling between ferric and ferryl states that generates radical species that induce lipid peroxidation. We demonstrate in vitro that acetaminophen inhibits hemoprotein-induced lipid peroxidation by reducing ferryl heme to its ferric state and quenching globin radicals. Severe muscle injury (rhabdomyolysis) is accompanied by the release of myoglobin that becomes deposited in the kidney, causing renal injury. We previously showed in a rat model of rhabdomyolysis that redox cycling between ferric and ferryl myoglobin yields radical species that cause severe oxidative damage to the kidney. In this model, acetaminophen at therapeutic plasma concentrations significantly decreased oxidant injury in the kidney, improved renal function, and reduced renal damage. These findings also provide a hypothesis for potential therapeutic applications for acetaminophen in diseases involving hemoprotein-mediated oxidative injury.

KCNJ10 gene mutations causing EAST syndrome (epilepsy, ataxia, sensorineural deafness, and tubulopathy) disrupt channel function.

Mutations of the KCNJ10 (Kir4.1) K(+) channel underlie autosomal recessive epilepsy, ataxia, sensorineural deafness, and (a salt-wasting) renal tubulopathy (EAST) syndrome. We investigated the localization of KCNJ10 and the homologous KCNJ16 in kidney and the functional consequences of KCNJ10 mutations found in our patients with EAST syndrome. Kcnj10 and Kcnj16 were found in the basolateral membrane of mouse distal convoluted tubules, connecting tubules, and cortical collecting ducts. In the human kidney, KCNJ10 staining was additionally observed in the basolateral membrane of the cortical thick ascending limb of Henle's loop. EM of distal tubular cells of a patient with EAST syndrome showed reduced basal infoldings in this nephron segment, which likely reflects the morphological consequences of the impaired salt reabsorption capacity. When expressed in CHO and HEK293 cells, the KCNJ10 mutations R65P, G77R, and R175Q caused a marked impairment of channel function. R199X showed complete loss of function. Single-channel analysis revealed a strongly reduced mean open time. Qualitatively similar results were obtained with coexpression of KCNJ10/KCNJ16, suggesting a dominance of KCNJ10 function in native renal KCNJ10/KCNJ16 heteromers. The decrease in the current of R65P and R175Q was mainly caused by a remarkable shift of pH sensitivity to the alkaline range. In summary, EAST mutations of KCNJ10 lead to impaired channel function and structural changes in distal convoluted tubules. Intriguingly, the metabolic alkalosis present in patients carrying the R65P mutation possibly improves residual function of KCNJ10, which shows higher activity at alkaline pH.

Nephrocalcinosis (enamel renal syndrome) caused by autosomal recessive FAM20A mutations.

BACKGROUND/AIMS: Calcium homeostasis requires regulated cellular and interstitial systems interacting to modulate the activity and movement of this ion. Disruption of these systems in the kidney results in nephrocalcinosis and nephrolithiasis, important medical problems whose pathogenesis is incompletely understood. METHODS: We investigated 25 patients from 16 families with unexplained nephrocalcinosis and characteristic dental defects (amelogenesis imperfecta, gingival hyperplasia, impaired tooth eruption). To identify the causative gene, we performed genome-wide linkage analysis, exome capture, next-generation sequencing, and Sanger sequencing. RESULTS: All patients had bi-allelic FAM20A mutations segregating with the disease; 20 different mutations were identified. CONCLUSIONS: This autosomal recessive disorder, also known as enamel renal syndrome, of FAM20A causes nephrocalcinosis and amelogenesis imperfecta. We speculate that all individuals with biallelic FAM20A mutations will eventually show nephrocalcinosis.

Systematic review of accuracy of reporting of Congo red-stained amyloid in 2010-2020 compared with earlier.

BACKGROUND: Almost always, Congo red-stained amyloid between polariser and analyser is said to show "green birefringence" or "apple-green birefringence". In 2010, we found that not all published images showed green, and not all that did showed only green. This systematic review of more recent papers was to find if there had been any improvement in the accuracy of reporting. MATERIALS AND METHODS: MEDLINE was searched on 15 March 2021 for papers published between 2010 and 2020 inclusive mentioning amyloid and Congo red. These were examined for descriptions of colours, which were compared with images. Papers were searched for mentions of anomalous colours, errors in physical optics, and misquotation of references about polarisation. RESULTS: In 374 papers, there were 444 descriptions of colours, with 511 images in 257 papers. The commonest descriptions were apple-green, 249/444 (56%), and green, 105/444 (24%). The description agreed with colours seen in 116/511 images (23%) (previously 64/191, 34%). Green was seen in 342/511 images (67%) (previously 159/191, 83%), but not in 169/511 (33%), although each image was reported to show green. Green alone was seen in 103/511 images (20%) (previously 59/191, 31%), and was combined with at least one other colour in 239/511 (47%). Ten papers included the term anomalous. Eight papers incorrectly said that there was green dichroism, three incorrectly used the term green metachromasia, and two incorrectly mentioned green fluorescence. Twenty-seven papers misquoted references. CONCLUSIONS: There is widespread and increasing inaccuracy of reporting of colours seen in Congo red-stained amyloid. People persist in saying "green birefringence" or "apple-green birefringence", even when no green is seen, or there are also other colours. Few appear to appreciate that the other colours are genuine, respectable, and helpful, the physical optical principles that explain the colours are now understood, and the best expression to use is anomalous colours.KEY MESSAGE"Green birefringence" and "apple-green birefringence" are inappropriate terms to describe the findings in amyloid stained with Congo red and examined between crossed polariser and analyser, because green is not always seen, and even when it is, other colours are commonly seen as well. The proportions of colour images showing any green and green alone, and the proportion of descriptions that agreed with illustrated colours, significantly decreased in 2010-2020 compared with earlier. The most appropriate and scientific description of the findings is anomalous colours.

CD248+ stromal cells are associated with progressive chronic kidney disease.

Stromal fibroblasts are the primary cells of the kidney that produce fibrotic matrix. CD248 is a stromal marker expressed on fibroblasts and pericytes within the human kidney. Here, we tested whether CD248 expression in the kidney colocalizes with fibrosis and if it is associated with known determinants of chronic kidney disease (CKD). CD248 expression was located and quantified in situ by immunohistochemistry in kidney biopsies from 93 patients with IgA nephropathy and compared with 22 archived biopsies encompassing normal kidney tissue as control. In normal kidney tissue, CD248 was expressed by resident pericytes, stromal fibroblasts, and was upregulated in human CKD. The expression was linked to known determinants of renal progression. This relationship was maintained in a multivariate analysis with CD248 expression linked to renal survival. CD248 was expressed by a population of α-smooth muscle actin (SMA)(+) myofibroblasts and α-SMA(-) stromal cells but not expressed on CD45(+) leukocytes. Thus, CD248 defines a subset of stromal cells, including but not limited to some myofibroblasts, linked to albuminuria and tubulointerstitial damage during tissue remodeling in CKD.

Effect of angiotensin II and its receptor antagonists on human corpus cavernous contractility and oxidative stress: modulation of nitric oxide mediated relaxation.

PURPOSE: To our knowledge the interaction between angiotensin II and nitric oxide in the control of human corpus cavernous function has not been assessed previously. We determined the presence and role of angiotensin II and its receptors in human penile function. MATERIALS AND METHODS: Corpus cavernous tissue was obtained from 35 patients undergoing gender reassignment surgery. Immunohistochemical analysis was done to determine angiotensin II peptide tissue distribution. Organ bath studies were done to determine the angiotensin II/nitric oxide interaction on corpus cavernous smooth muscle function. The role of oxidative stress in the angiotensin II response was also examined using the nicotinamide adenine dinucleotide phosphate oxidase inhibitor apocynin. RESULTS: Angiotensin II was distributed in arteriolar endothelium, endothelium lining sinusoids and smooth muscle cells, and caused dose dependent contraction of human corpus cavernous smooth muscle strips that was inhibited by the angiotensin type 1 receptor antagonist losartan. Relaxation of corpus cavernous smooth muscle induced by the nitric oxide donor sodium nitroprusside or electrical field stimulation was potentiated by losartan. Apocynin decreased angiotensin II induced corpus cavernous contraction. CONCLUSIONS: Angiotensin II and nitric oxide interact to modulate human cavernous function since losartan potentiated sodium nitroprusside and electrical field stimulation mediated corpus cavernous smooth muscle relaxation. The angiotensin II response involves the production of superoxide and the development of oxidative stress. These findings support the role of angiotensin II in the regulation of human penile smooth muscle tone and suggest that angiotensin type 1 receptor inhibition may be a therapeutic approach to erectile dysfunction.

Problems with 'focal segmental glomerulosclerosis'.

The term 'focal segmental glomerulosclerosis (FSGS)' has been applied to many different conditions. All classifications of 'FSGS', including those describing 'variants', perpetuate the misconceptions that the entities included have something in common and that the term 'FSGS' has some value. With a rigorous approach to renal biopsies showing segmental lesions, especially with knowledge of clinical circumstances and with detailed analysis of features such as the appearance of lesions and their position within glomeruli, a pathologist can provide information that is clinically more useful than merely the bald diagnosis 'FSGS'. More precise terms should be used. 'Overload changes' can be used to describe the changes seen in reduced renal mass. 'Tip changes' can be seen in many conditions and are not a disease in themselves. 'The glomerular tip lesion as originally defined' means the occurrence of tip changes in otherwise normal glomeruli, in the nephrotic syndrome. 'Early classical segmental sclerosing glomerulopathy' is the combination of tip changes and otherwise abnormal glomeruli, in the nephrotic syndrome. 'Late classical segmental sclerosing glomerulopathy' means segmental lesions at various sites within glomeruli, in the nephrotic syndrome. 'Collapsing glomerulopathy' is distinctive, and its inclusion in classifications emphasises the lack of specificity of 'FSGS'.

Immune profile and Epstein-Barr virus infection in acute interstitial nephritis: an immunohistochemical study in 78 patients.

BACKGROUND: Acute interstitial nephritis (AIN) is a common cause of acute kidney injury and is characterised by a dense interstitial cellular infiltrate, which has not been well defined. Previous studies have demonstrated a correlation between Epstein-Barr virus (EBV) infection and AIN. The purpose of our study was to define the nature of the interstitial immune infiltrate and to investigate the possibility of renal infection with EBV. METHODS: Seventy-eight patients with AIN were identified from renal biopsy reports in a single centre over an 18-year period. Immunohistochemical staining was performed to define the cellular infiltrate. In situ hybridization and immunohistology were used to detect EBV. RESULTS: A positive correlation between CD68 macrophage infiltration and serum creatinine concentration at presentation was identified. IL-4, eotaxin, CCR3, CCR5 and VCAM-1 were all expressed in biopsies of AIN. Using in situ hybridization and immunohistochemistry, EBV was not detected in any of the AIN sections analysed. CONCLUSION: This study has assessed the nature of the interstitial infiltrate in AIN. EBV was not detected in the renal biopsies, suggesting that EBV is not a pathogenetic factor in AIN.