Akira Ashida

Clinical practice guideline for the management of chronic kidney disease-mineral and bone disorder

Masafumi Fukagawa, Keitaro Yokoyama, Fumihiko Koiwa, Masatomo Taniguchi, Tetsuo Shoji, Junichiro James Kazama, Hirotaka Komaba, Ryoichi Ando, Takatoshi Kakuta, Hideki Fujii, Msasaaki Nakayama, Yugo Shibagaki, Seiji Fukumoto, Naohiko Fujii, Motoshi Hattori, Akira Ashida, Kunitoshi Iseki, Takashi Shigematsu, Yusuke Tsukamoto, Yoshiharu Tsubakihara, Tadashi Tomo, Hideki Hirakata, and Tadao Akizawa for CKD-MBD Guideline Working Group, Japanese Society for Dialysis Therapy

Analysis of genetic and predisposing factors in Japanese patients with atypical hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal impairment. Approximately 10% of cases are classified as atypical due to the absence of Shiga toxin-producing bacteria as a trigger. Uncontrolled activation of the complement system plays a role in the pathogenesis of atypical HUS (aHUS). Although many genetic studies on aHUS have been published in recent years, only limited data has been gathered in Asian countries. We analyzed the genetic variants of 6 candidate genes and the gene deletion in complement factor H (CFH) and CFH-related genes, examined the prevalence of CFH autoantibodies and evaluated the genotype-phenotype relationship in 10 Japanese patients with aHUS. We identified 7 causative or potentially causative mutations in CFH (p.R1215Q), C3 (p.R425C, p.S562L, and p.I1157T), membrane cofactor protein (p.Y189D and p.A359V) and thrombomodulin (p.T500M) in 8 out of 10 patients. All 7 of the mutations were heterozygous and four of them were novel. Two patients carried CFH p.R1215Q and 3 other patients carried C3 p.I1157T. One patient had 2 causative mutations in different genes. One patient was a compound heterozygote of the 2 MCP mutations. The patients carrying mutations in CFH or C3 had a high frequency of relapse and a worse prognosis. One patient had CFH autoantibodies. The present study identified the cause of aHUS in 9 out of 10 Japanese patients. Since the phenotype-genotype correlation of aHUS has clinical significance in predicting renal recovery and transplant outcome, a comprehensively accurate assessment of molecular variation would be necessary for the proper management of aHUS patients in Japan.

Functional characterization of LMX1B mutations associated with nail-patella syndrome

Nail-patella syndrome (NPS) is an autosomal dominant disease characterized by dysplastic nails, absent or hypoplastic patellae, elbow dysplasia, and nephropathy. Recently, it was shown that NPS is the result of heterozygous mutations in the LIM-homeodomain gene, LMX1B. Subsequently, many mutations of the LMX1B gene have been reported in NPS patients. However, functional analyses of the mutant proteins have been performed in only a few mutations. Furthermore, the mechanisms of dominant inheritance in humans have not been established. In the present study, we analyzed the LMX1B gene in three Japanese patients with NPS and identified two novel mutations, 6 nucleotide deletion (Δ246Ν 247Q) and V242L. These two mutations are located in the homeodomain of LMX1B. Functional analyses of the LMX1B mutants revealed that these mutants had diminished transcriptional activity and had lost DNA binding ability. Furthermore, we demonstrated that each mutant did not manifest a dominant-negative effect on the transcriptional activity of wild-type LMX1B. These results suggested that NPS is caused by loss-of-function mutations of LMX1B, and haploinsufficiency of LMX1B should be the predominant pathogenesis of NPS in humans.

TWO CASES OF HYPONATREMIC-HYPERTENSIVE SYNDROME IN CHILDHOOD WITH RENOVASCULAR HYPERTENSION

We report two children with renovascular hypertension and fibromuscular dysplasia. They initially presented with severe hyponatremia, hypokalemia, polyuria, and transient proteinuria. This combination of symptoms is known to occur in patients with renovascular and malignant hypertension, and is known as hyponatremic-hypertensive syndrome (HHS), although it is considered rare in children. Since in both of our patients, the renal arterial stenosis was very severely or almost totally occlusive, we could not perform percutaneous transluminal renal artery angioplasty, and therefore nephrectomy was the only option. A histological study showed partial or complete occlusion with intimal hyperplasia and medial fibroplasia of intrarenal arteries such as the interlobular arteries. Conclusion: Both patients showed rapidly progressive renovascular hypertension and loss of function of the affected kidney. In order to preserve renal function in such cases, early invasive intervention appears to be necessary.

Diagnostic criteria for atypical hemolytic uremic syndrome proposed by the Joint Committee of the Japanese Society of Nephrology and the Japan Pediatric Society.

Atypical hemolytic uremic syndrome (aHUS) is rare and comprises the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. Recently, abnormalities in the mechanisms underlying complement regulation have been focused upon as causes of aHUS. The prognosis for patients who present with aHUS is very poor, with the first aHUS attack being associated with a mortality rate of approximately 25%, and with approximately 50% of cases resulting in end‐stage renal disease requiring dialysis. If treatment is delayed, there is a high risk of this syndrome progressing to renal failure. Therefore, we have developed diagnostic criteria for aHUS to enable its early diagnosis and to facilitate the timely initiation of appropriate treatment. We hope these diagnostic criteria will be disseminated to as many clinicians as possible and that they will be used widely.

2015 Japanese Society for Dialysis Therapy: Guidelines for Renal Anemia in Chronic Kidney Disease

Renal anemia is a complication of chronic kidney disease. Guidelines for safe and effective treatment in patients with renal anemia are needed. The Japanese Society for Dialysis Therapy (JSDT) published guidelines for the treatment of renal anemia in chronic hemodialysis patients in 2004 and in hemodialysis, peritoneal dialysis, predialysis, and pediatric patients in 2008. These two publications provide excellent guidance with respect to clinical practice issues, including the definition and diagnosis of renal anemia, the criteria for the initiation of treatment, target hemoglobin levels, iron supplementation therapy, blood transfusion, and side effects. The guidelines significantly improved the treatment of renal anemia in Japan. However, since 2008, many studies have assessed the treatment of renal anemia, and erythropoiesis-stimulating agents (ESAs) are now available. Therefore, the Executive Board of the JSDT decided that it was time to revise the guidelines to make them more appropriate to the situation of chronic kidney disease patients in Japan. This is the third edition of the guidelines for renal anemia published by the JSDT. The purpose is to improve the prognosis of chronic kidney disease patients, including after renal transplantation, through the treatment of renal anemia. The intended users of the guidelines are all healthcare professionals engaged in the treatment of chronic kidney disease. Regarding the treatment of adult dialysis and predialysis patients, statements and commentary are provided in the context of answers to clinical questions in Chapter 2 (Target Hb level and criteria for starting renal anemia treatment) and Chapter 4 (Evaluation of iron status and iron therapy). Furthermore, the essential information is provided alongside the critical issues in Chapter 1 (Diagnosis of renal anemia), Chapter 3 (Administration of ESAs—administration route and dose), Chapter 5 (ESA hyporesponsiveness), Chapter 6 (Side effects and concomitant symptoms of ESAs), and Chapter 7 (Red blood cell transfusion). In addition, the treatment of pediatric patients and post-renal transplant patients is discussed in Chapter 8 and Chapter 9, respectively.

Clinical guides for atypical hemolytic uremic syndrome in Japan

Atypical hemolytic uremic syndrome (aHUS) is a rare disease characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. In 2013, we developed diagnostic criteria to enable early diagnosis and timely initiation of appropriate treatment for aHUS. Recent clinical and molecular findings have resulted in several proposed classifications and definitions of thrombotic microangiopathy and aHUS. Based on recent advances in this field and the emerging international consensus to exclude secondary TMAs from the definition of aHUS, we have redefined aHUS and proposed diagnostic algorithms, differential diagnosis, and therapeutic strategies for aHUS.

Clinical characteristics of obstructive uropathy associated with rotavirus gastroenteritis in Japan.

AIMS Rotavirus gastroenteritis is severe and often results in dehydration and pre-renal azotemia. However, we have encountered four children with acute obstructive uropathy associated with acute rotavirus gastroenteritis, and several similar cases have been reported. Therefore, the aim of the present study was to clarify the epidemiology and clinical features of acute obstructive uropathy associated with acute rotavirus gastroenteritis in Japanese children. PATIENTS AND METHODS We sent questionnaires to all members of the Japanese Society for Nephrology and all authors who had published case reports of this disease in Japan, inquiring about patient age at diagnosis, sex, the type of stones, laboratory data and other factors. RESULTS 21 reported patients were evaluable, ranging from 0.4 to 3 years. The sex distribution showed a strong male prevalence. Oliguria had appeared about 7 days after the onset of gastroenteritis. Most of the patients showed hyperuricemia and hyponatremia. The stones consisted mainly of ammonium acid urate. The patients were discharged with normal renal function. CONCLUSION Although obstructive uropathy associated with rotavirus gastroenteritis is very rare, this disease condition should be explored when anuria is refractory to sufficient fluid replacement therapy or when oliguria persists despite recovery of the gastrointestinal symptoms.

Four cases of postrenal renal failure induced by renal stone associated with rotavirus infection

Rotavirus (RV) is a common pathogen that causes acute gastroenteritis in childhood. Some cases with RV infection also have prerenal renal failure induced by dehydration associated with vomiting and diarrhea. Here, we report 4 patients with RV infection who developed postrenal renal failure induced by urinary tract obstruction with uroammoniac calculi or crystals. The patients did not have metabolic disorders or abnormalities of the urinary tract, and increased urinary excretion of uric acid was not recognized at discharge. In addition, no abnormalities in the uric acid transporter (URAT1) were found in any of the patients. Uric acid stone formation was considered to have originated from the low pH caused by dehydration and the increase of urinary uric acid excretion from damaged cells.

Oxidative stress in a rat model of nephrosis can be quantified by electron spin resonance

The pathogenesis of nephrotic syndrome is not clear. In this study, we used electron spin resonance (ESR) to evaluate levels of reactive oxygen species in rats with puromycin aminonucleoside (PAN)-induced nephrosis. Twenty-six Wistar rats were divided into four groups: (1) PAN treated, (2) PAN treated and α-tocopherol supplemented, (3) supplemented with α-tocopherol only, (4) control. On day 9, urinary protein excretion was measured. On day 10, all animals were sacrificed with retrograde perfusion via the aorta to obtain renal venous perfusates. The signal intensities of ascorbate radicals in the perfusates were determined by ESR. After perfusion, the kidneys were isolated and sieved to obtain glomeruli for determination of glomerular thiobarbituric acid-reactive substance (TBArs) and α-tocopherol. Urinary protein excretion by PAN-treated rats increased significantly on day 9 and was reduced by α-tocopherol supplementation. The ascorbate radical intensity and glomerular TBArs level were higher in PAN-treated than in control rats and were both suppressed to control levels by α-tocopherol supplementation. There were positive correlations between ascorbate radical intensity and the daily urinary protein, as well as between ascorbate radical intensity and the glomerular TBArs level. Hence, it is possible to quantify oxidative stress due to PAN nephrosis by ESR. Our findings suggest that lipid peroxidation plays an important role in the pathogenesis of proteinuria in PAN-treated rats.