Cilostazol-induced acute tubulointerstitial nephritis accompanied by IgA nephropathy: a case report.

BACKGROUND: Cilostazol is an antiplatelet drug that is widely prescribed for the prevention of secondary stroke. Adverse reactions to cilostazol include headaches, palpitations, and diarrhea. Little is known about the nephrotoxicity of cilostazol, such as acute kidney injury. We report a biopsy-proven case of diffuse tubulointerstitial nephritis induced by cilostazol. CASE PRESENTATION: A 69-year-old woman prescribed cilostazol was hospitalized for acute kidney injury. On admission, her renal function deteriorated, with an increased serum creatinine level. Urinalysis showed hematuria, proteinuria, and hyper-beta2-microglobulinuria. A renal biopsy revealed diffuse tubulointerstitial nephritis associated with IgA nephropathy, and gallium-67 scintigraphy showed uptake in the bilateral kidneys. A drug lymphocyte stimulation test for cilostazol was positive, and the patient was diagnosed with cilostazol-induced acute tubulointerstitial nephritis. Despite discontinuation of cilostazol, her renal function rapidly worsened and steroid pulse therapy was initiated, followed by oral high-dose glucocorticoid therapy. After steroid treatment, her serum creatinine level normalized in parallel with urine beta2-microglobulin. CONCLUSION: Cilostazol can induce acute tubulointerstitial nephritis.

Prognostic factors for mortality in middle-aged and older hemodialysis patients: a 5-year observational study.

Clinical guidelines for hemodialysis therapy have been described in an evidence-based manner with most evidence from randomized control trials or retrospective studies in which all generations of the hemodialysis patients were enrolled. Therefore, the question still remains whether these guidelines can be applied to increasing older patients. This study is an observational study, including 735 patients who received maintenance hemodialysis in April 2006. At baseline, the participants' age was 62.1 ± 12.8 years (mean ± SD). Hemodialysis duration was 103.7 ± 89.3 months. In a 5-year observation period (actual follow-up period: 1551 ± 499 days), 175 patients died. Prognostic factors were investigated by multivariate analysis with Cox proportional hazard model. Next, we stratified the patients according to their age. 363 patients were included in the middle-aged patient's category between 40 and 64 years, and 314 were involved in the older patient's category between 65 and 84 years old. As a subanalysis, significant predictors of 5-year survival were examined in the age-stratified cohort. Then, Kt/V, serum ß2-microglobulin and calcium concentration were significant predictors in our entire cohort, as well as body mass index, neutrophil count, and serum sodium concentration even after adjustment for age, gender, diabetic status and hemodialysis duration. However, Kt/V, serum ß2-microglobulin and calcium concentration controlled by hemodialysis prescriptions were independent risk factors especially in older patients, not in middle-aged patients. In conclusion, hemodialysis prescriptions for lowering uremic toxins and managing mineral-bone disorder are important to decrease the risk of death even in older hemodialysis patients.

Mesangial Cell Mammalian Target of Rapamycin Complex 1 Activation Results in Mesangial Expansion.

Human glomerular diseases can be caused by several different diseases, many of which include mesangial expansion and/or proliferation followed by glomerulosclerosis. However, molecular mechanisms underlying the pathologic mesangial changes remain poorly understood. Here, we investigated the role of the mammalian target of rapamycin complex 1 (mTORC1)-S6 kinase pathway in mesangial expansion and/or proliferation by ablating an upstream negative regulator, tuberous sclerosis complex 1 (TSC1), using tamoxifen-induced Foxd1-Cre mice [Foxd1ER(+) TSC1 mice]. Foxd1ER(+) TSC1 mice showed mesangial expansion with increased production of collagen IV, collagen I, and α-smooth muscle actin in glomeruli, but did not exhibit significant mesangial proliferation or albuminuria. Furthermore, rapamycin treatment of Foxd1ER(+) TSC1 mice suppressed mesangial expansion. Among biopsy specimens from patients with glomerular diseases, analysis of phosphorylated ribosomal protein S6 revealed mesangial cell mTORC1 activation in IgA nephropathy and in lupus mesangial proliferative nephritis but not in the early phase of diabetic nephropathy. In summary, mesangial cell mTORC1 activation can cause mesangial expansion and has clinical relevance for human glomerular diseases. This report also confirms that the tamoxifen-induced mesangium-specific Cre-loxP system is useful for studies designed to clarify the role of the mesangium in glomerular diseases in adults.

Successful treatment of highly advanced immunoglobulin G4-related kidney disease presenting renal mass-like regions with end-stage kidney failure: a case study.

BACKGROUND: Immunoglobulin G4-related kidney disease characterized by immunoglobulin G4-positive plasma cell-rich tubulointerstitial nephritis has distinctive serological and radiological findings. Renal prognosis is good because of a good response to glucocorticoids. Here we report a case of successful treatment of highly advanced immunoglobulin G4-related kidney disease presenting renal mass-like regions with end-stage kidney failure. CASE PRESENTATION: A 59-year-old Japanese man was referred to our hospital because of uremia with a creatinine level of 12.36 mg/dL. Urinalysis revealed mild proteinuria and hyperß2microglobulinuria, and blood tests showed hyperglobulinemia with an IgG level of 3243 mg/dL and an IgG4 level of 621 mg/dL. Non-contrast computed tomography revealed renal mass-like regions. Based on the findings, immunoglobulin G4-related kidney disease was suspected, however, further radiological examination showed unexpected results. Ga-67 scintigraphy showed no kidney uptake. T2-weighted magnetic resonance imaging revealed high-intensity signals which corresponded to mass-like regions and multiple patchy low-intensity signals in kidney cortex. Finally, the patient was diagnosed with immunoglobulin G4-related kidney disease by renal pathology of severe immunoglobulin G4-positive plasma cell-rich tubulointerstitial nephritis and characteristic fibrosis. He received 50 mg oral prednisolone, which was tapered with a subsequent decrease of serum creatinine and IgG4 levels. One year after initiation of treatment, he achieved normalization of serum IgG4 level and proteinuria, and remained off dialysis with a creatinine level of 3.50 mg/dL. After treatment with steroids, repeat imaging suggested bilateral severe focal atrophy. However, mass-like regions did not show atrophic change although renal atrophy was evident in patchy low-intensity lesions on T2-weighted magnetic resonance imaging. These findings suggest that multiple patchy low-intensity signals and high-intensity mass-like regions were mildly atrophic lesions of immunoglobulin G4-related kidney disease due to severe fibrosis and normal parts of kidney, respectively. CONCLUSIONS: In immunoglobulin G4-related kidney disease with severe kidney failure, radiological findings should be carefully examined. In addition, renal prognosis may be good despite highly advanced tubulointerstitial nephritis and fibrosis.

Re-evaluation of Pre-pump Arterial Pressure to Avoid Inadequate Dialysis and Hemolysis: Importance of Prepump Arterial Pressure Monitoring in Hemodialysis Patients.

Prepump arterial pressure (PreAP) is monitored to avoid generating excessive negative pressure. The National Kidney Foundation K/DOQI clinical practice guidelines for vascular access recommend that PreAP should not fall below -250 mm Hg because excessive negative PreAP can lead to a decrease in the delivery of blood flow, inadequate dialysis, and hemolysis. Nonetheless, these recommendations are consistently disregarded in clinical practice and pressure sensors are often removed from the dialysis circuit. Thus far, delivered blood flow has been reported to decrease at values more negative than -150 mm Hg of PreAP. These values have been analyzed by an ultrasonic flowmeter and not directly measured. Furthermore, no known group has evaluated whether PreAP-induced hemolysis occurs at a particular threshold. Therefore, the aim of this study was to clarify the importance of PreAP in the prediction of inadequate dialysis and hemolysis. By using different diameter needles, human blood samples from healthy volunteers were circulated in a closed dialysis circuit. The relationship between PreAP and delivered blood flow or PreAP and hemolysis was investigated. We also investigated the optimal value for PreAP using several empirical monitoring methods, such as a pressure pillow. Our investigation indicated that PreAP is a critical factor in the determination of delivered blood flow and hemolysis, both of which occured at pressure values more negative than -150 mm Hg. With the exception of direct pressure monitoring, commonly used monitoring methods for PreAP were determined to be ineffective. We propose that the use of a vacuum monitor would permit regular measurement of PreAP.

Polymorphism in the human matrix Gla protein gene is associated with the progression of vascular calcification in maintenance hemodialysis patients.

BACKGROUND: Matrix Gla protein (MGP) is one of the important proteins inhibiting vascular calcification (VC). Single nucleotide polymorphisms (SNPs) located in the promoter and coding regions of the MGP gene affect the transcriptional activity. In this study, we investigated the relationship between the SNPs and progression of VC in patients undergoing maintenance hemodialysis (MHD). METHODS: This was a retrospective, longitudinal cohort study of 134 MHD patients whose VC could be followed by multi-detector computed tomography (MDCT) examinations. MGP-SNPs (T-138C, rs1800802 and G-7A, rs1800801) were determined. The progression speed of VC was examined by plotting the abdominal aortic calcium volume scores. RESULTS: The progression speed of VC of patients with the CC genotype of T-138C was significantly slower than that of patients with the CT or TT genotype. Multiple regression analysis showed that CT/TT genotype, greater age at the beginning of MHD, male sex, high levels of calcium × phosphate, low levels of high-density lipoprotein cholesterol, high levels of low-density lipoprotein cholesterol, low levels of ferritin and non-use of angiotensin II receptor blockers were significantly associated with progression of VC. CONCLUSIONS: The MGP-138CC genotype may be associated with slower progression of VC in MHD patients. The genotype of the MGP gene will be a genomic biomarker that is predictive of VC progression.

SOX9 protein induces a chondrogenic phenotype of mesangial cells and contributes to advanced diabetic nephropathy.

Diabetic nephropathy (DN) is the most important chronic kidney disease. We previously reported that Smad1 transcriptionally regulates the expression of extracellular matrix in DN. Phenotypic change in mesangial cells (MCs) is a key pathologic event in the progression of DN. The aim of this study is to investigate a novel mechanism underlying chondrogenic phenotypic change in MCs that results in the development of DN. MCs showed chondrogenic potential in a micromass culture, and BMP4 induced the expression of chondrocyte markers (SRY-related HMG Box 9 (SOX9) and type II collagen (COL2)). Advanced glycation end products induced the expression of chondrocyte marker proteins downstream from the BMP4-Smad1 signaling pathway in MCs. In addition, hypoxia also induced the expression of BMP4, hypoxia-inducible factor-1α (HIF-1α), and chondrocyte markers. Overexpression of SOX9 caused ectopic expression of proteoglycans and COL2 in MCs. Furthermore, forced expression of Smad1 induced chondrocyte markers as well. Dorsomorphin inhibited these inductions. Glomerular expressions of HIF-1α, BMP4, and chondrocyte markers were observed in diabetic nephropathy mice. These positive stainings were observed in mesangial sclerotic lesions. SOX9 was partially colocalized with HIF-1α and BMP4 in diabetic glomeruli. BMP4 knock-in transgenic mice showed not only similar pathological lesions to DN, but also the induction of chondrocyte markers in the sclerotic lesions. Here we demonstrate that HIF-1α and BMP4 induce SOX9 expression and subsequent chondrogenic phenotype change in DN. The results suggested that the transdifferentiation of MCs into chondrocyte-like cells in chronic hypoxic stress may result in irreversible structural change in DN.

MPO-ANCA-positive anti-glomerular basement membrane antibody disease successfully treated by plasma exchange and immunosuppressive therapy.

Anti-glomerular basement membrane (GBM) antibody disease is clinically manifested as rapidly progressive glomerulonephritis (RPGN) with crescentic changes. The renal prognosis is poor. We report here the case of a 61-year-old woman with myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA)-positive anti-GBM antibody disease. This patient was referred to our hospital because of RPGN. Anti-GBM antibody was positive with a titer of 38 EU. The MPO-ANCA titer was 65 EU. Chest imaging examination revealed pulmonary multiple nodules. ANCA-associated vasculitis was suspected. Renal pathology revealed cellular crescents in 13 out of 17 glomeruli. Immunofluorescence with anti-IgG antibody, anti-C3 antibody, and anti-fibrin antibody showed linear staining along the glomerular capillary walls. Based on these findings, the patient was diagnosed with anti-GBM antibody disease. Hemodialysis was started because of uremic syndrome with elevated serum creatinine (6.84 mg/dL). In addition, treatment with plasma exchange using 3.6 L (90 mL/kg) of fresh frozen plasma combined with an oral dose of 40 mg of prednisolone was initiated. Within 3 weeks, both types of autoantibodies became undetectable. Subsequently, this patient achieved dialysis independence and remission of glomerulonephritis. No adverse effects were observed. In patients with MPO-ANCA-positive anti-GBM antibody disease, intensive therapy predominantly with plasma exchange might be operative, even though renal function is less likely to recover.

An autopsy case of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with intestinal bleeding in chronic renal failure.

A 50-year-old man who underwent hemodialysis (HD) at local outpatient HD center due to end-stage renal disease (ESRD) was transferred to our hospital because of pneumonia. He had severe emaciation and past history of congestive heart failure. Presenting symptoms almost consistently involved difficulty in hearing and recurrent attacks of migraine-like headaches. He was diagnosed with dilated cardiomyopathy, showing diastolic mechanical dyssynchrony by tissue Doppler echocardiography. On the day of death, he had hematemesis and hemorrhagic shock. Autopsy revealed perforation of duodenum, and genetic analysis using mitochondrial DNA from cardiac muscle and iliopsoas muscle revealed a 3243A > G mutation in the mitochondrial tRNA(Leu(UUR)) gene, which is related to mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Multiple organ failure due to the mutation of mitochondrial DNA with gastrointestinal bleeding is not a common.

[Case of renal artery stenosis in an elderly patient after nephrectomy diagnosed by ultrasound sonography, showing improvement of blood pressure and renal dysfunction after renal artery stenting].

Arteriosclerotic renal artery stenosis is one of the increasingly common diseases that affects many aged patients. There are various non-invasive methods to diagnose renal artery stenosis, such as contrast enhanced CT or MRI. However, these methods are not appropriate for patients with renal dysfunction. Ultrasound sonography is becoming one of the promising methods to diagnose artery stenosis because of photographic improvements. In this case, a 72-year-old woman was hospitalized 7 months after nephrectomy because of severe hypertension, heart failure and kidney dysfunction. The heart failure was quite uncontrollable in spite of massive administration of diuretics, and finally, hemodialysis was started to control her volume status. In consideration of her past history and abdominal bruit, we evaluated the renal artery stenosis by ultrasound sonography and confirmed the diagnosis by renal angiography. To improve hypertension control, we performed renal artery stenting, which resulted in an impressive improvement of her blood pressure and renal function. We recognized the importance of careful causal evaluation of renal dysfunction, even though it is difficult to apply invasive therapy to patients after nephrectomy.

Angio-embolization of renal artery pseudoaneurysm after renal biopsy: a case report.

Renal artery pseudoaneurysm is a rare clinical entity that has been reported after renal biopsy, percutaneous renal surgery, penetrating trauma, and rarely blunt renal trauma. We present the case of a 37-year-old man with ruptured renal artery pseudoaneurysm accompanied by massive gross hematuria, urinary clot retention, and bladder tamponade, which were the presenting signs seven hours after renal biopsy. Abdominal CT scan showed a large perinephric, intracapsular hematoma of left kidney. His angiogram revealed a left renal segmental artery pseudoaneurysm that measured 1 cm x 1 cm. He was successfully treated by selective embolization of the arterial branch supplying the pseudoaneurysm.

Involvement of Elf3 on Smad3 activation-dependent injuries in podocytes and excretion of urinary exosome in diabetic nephropathy.

Diabetic nephropathy (DN) is among the most serious complications of diabetes mellitus, and often leads to end-stage renal disease ultimately requiring dialysis or renal transplantation. The loss of podocytes has been reported to have a role in the onset and progression of DN. Here, we addressed the activation mechanism of Smad3 signaling in podocytes. Expression of RII and activation of Smad3 were induced by AGE exposure (P<0.05). Reduction of the activation of RII-Smad3 signaling ameliorated podocyte injuries in Smad3-knockout diabetic mice. The bone morphogenetic protein 4 (BMP4) significantly regulated activation of RII-Smad3 signalings (P<0.05). Moreover, the epithelium-specific transcription factor, Elf3was induced by AGE stimulation and, subsequently, upregulated RII expression in cultured podocytes. Induction of Elf3 and activation of RII-Smad3 signaling, leading to a decrease in WT1 expression, were observed in podocytes in diabetic human kidneys. Moreover, AGE treatment induced the secretion of Elf3-containing exosomes from cultured podocytes, which was dependent on the activation of the TGF-ß-Smad3 signaling pathway. In addition, exosomal Elf3 protein in urine could be measured only in urinary exosomes from patients with DN. The appearance of urinary exosomal Elf3 protein in patients with DN suggested the existence of irreversible injuries in podocytes. The rate of decline in the estimated Glomerular Filtration Rate (eGFR) after measurement of urinary exosomal Elf3 protein levels in patients with DN (R2 = 0.7259) might be useful as an early non-invasive marker for podocyte injuries in DN.

Systemic Sarcoidosis Presenting with Renal Involvement Caused by Various Sarcoidosis-associated Pathophysiological Conditions.

A 61-year-old man was diagnosed with sarcoidosis involving the lungs, eyes, parotid gland and extrathoracic lymph nodes complicated by chronic kidney injury and hypercalcemia. Kidney biopsy showed non-specific interstitial nephritis and nephrosclerosis. However, immunohistochemical staining of cell surface markers revealed a multinucleated giant macrophage surrounded by T-cells, suggesting granulomatous interstitial nephritis. Corticosteroid improved the kidney function, and reduced the serum levels of calcium and angiotensin-converting enzyme. Sarcoid nephropathy may be caused by the combination of several sarcoidosis-associated pathophysiological conditions and a comprehensive kidney examination should be performed to assess the type of injury when determining a treatment strategy.

IgA Nephropathy after Nivolumab Therapy for Postoperative Recurrence of Lung Squamous Cell Carcinoma.

Immune checkpoint inhibitors (ICIs) are becoming a common and important cancer therapy. ICIs are associated with a unique category of side effects, termed immune-related adverse events (irAEs). We herein report the case of a 72-year-old man with postoperative recurrence of lung squamous cell carcinoma who was treated with nivolumab and who developed proteinuria and a worsening kidney function. A kidney biopsy revealed IgA nephropathy. After drug withdrawal, the proteinuria improved and the deterioration of the patient's renal function was halted. Although renal irAEs are considered to be rare and glomerulonephritis is not typical presentation, physicians need to pay more attention to renal irAEs and glomerular injury.

Progressive renal insufficiency related to ALK inhibitor, alectinib.

Alectinib is a second generation anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor and is generally effective and tolerated in patients who have demonstrated disease progression or adverse effects while on the first generation inhibitor, crizotinib. ALK inhibitors can cause a reversible chronic increase of serum creatinine concentration; however, they rarely induce progressive renal insufficiency. We herein report a case of a 68-year-old woman diagnosed with ALK-positive advanced non-small cell lung cancer and who received ALK inhibitors. Due to dysgeusia and transaminitis, her medication was switched from crizotinib to alectinib. Rapid progressive glomerulonephritis developed 1 year after the initiation of alectinib treatment. A renal biopsy revealed unique kidney lesions in both tubules and glomeruli. Glucocorticoid therapy partially reversed kidney impairment. However, re-administration of alectinib caused kidney dysfunction, which was improved by the cessation of alectinib. Our case suggests that much attention should be paid to kidney function when using ALK inhibitors.

Lambda Light Chain Non-crystalline Proximal Tubulopathy with IgD Lambda Myeloma.

Light Chain Proximal Tubulopathy (LCPT) is a rare form of paraprotein-related kidney disease in which monoclonal free light chains damage the proximal renal tubular epithelial cells. We herein report the case of a 78-year-old woman who presented with anemia and kidney dysfunction. Serum and urine protein electrophoresis analyses revealed a monoclonal IgD and λ free light chains. Proximal tubular injury and the accumulation of λ light chains were found by kidney biopsy. Electron microscopy revealed no organized structure suggestive of crystals. LCPT was caused by IgD lambda myeloma and bortezomib and dexamethasone therapy led to very good partial response (VGPR) without a worsening of the kidney function.

A Novel Method of DAPI Staining for Differential Diagnosis of Renal Amyloidosis.

Amyloidosis is often overlooked because its clinical manifestations can mimic those of more-common diseases. It is important to get a precise diagnosis as early as possible for the prevention of further organ damages. Amyloidosis is a disorder caused by deposition of insoluble abnormal amyloid. The kidney is a frequent site of amyloid deposition. The amyloid fibrils have a characteristic appearance and generate birefringence under polarized light when stained with the Congo red dye. Classification of amyloidosis is based on the precursor protein that forms the amyloid fibrils and the distribution of amyloid deposits as either systemic or localized. Involvement of amyloid fibrils in kidneys mainly occurs as amyloid light-chain (AL) or amyloid A (AA) amyloidosis. The potassium permanganate method with Congo red staining was once used widely to discriminate AL and AA amyloidoses, but this method has a problem of false positive results. We found that extracellular and cytoplasmic glomerular 4', 6-diamidino-2-phenylindole (DAPI)-positive areas were clearly consistent with amyloid deposition in AL amyloidosis. In contrast, the overlapping staining was not seen in AA amyloidosis. Therefore, we propose that DAPI staining readily distinguishes AL renal amyloidosis from AA renal amyloidosis as a simple and reproducible histochemical method. J. Med. Invest. 64: 217-221, August, 2017.

A case of rapid amelioration of hepatitis C virus-associated cryoglobulinemic membranoproliferative glomerulonephritis treated by interferon-free directly acting antivirals for HCV in the absence of immunosuppressant.

Mixed cryoglobulinemic syndrome, which is a systemic vasculitis characterized by the immune complex deposition in small- and medium-sized arteries and most often due to chronic hepatitis C virus (HCV) infection, sometimes clinically manifests as refractory glomerulonephritis or nephritic syndrome. Patients with mixed cryoglobulinemic nephropathy who have a rapidly progressive glomerulonephritis should receive immunosuppressive therapy. After disease stabilization, patients should receive concurrent therapy for the underlying HCV infection. The standard therapy of a chronic HCV infection is IFN monotherapy or IFN combined with ribavirin; however, after the introduction of direct-acting antivirals (DAAs), the standard therapy for patients with HCV genotype 1 has dramatically changed. We report a case of HCV-associated cryoglobulinemic membranoproliferative glomerulonephritis (MPGN) successfully treated by daclatasvir and asunaprevir, which are IFN-free DAAs for HCV, in combination with angiotensin II receptor blocker without immunosuppressive therapy. The patient developed severe nephrotic syndrome with progressive kidney dysfunction. Blood examination revealed a high copy number of HCV-RNA (6.4 log IU/mL, type 1), cryoglobulinemia, paraproteinemia of IgM-κ, and hypocomplementemia. Histological analysis showed MPGN type 1. These findings were compatible with those observed in HCV-associated cryoglobulinemic MPGN. This case offers original evidence for the application of newer generation of IFN-free DAAs in the treatment of HCV-associated cryoglobulinemic nephropathy.

Influential factors on serum albumin concentration in hospitalized chronic kidney disease patients.

BACKGROUND: Serum albumin concentration (SAC) is a prognostic factor that is affected by many factors such as postural change, liver function and food intake. Chronic kidney disease (CKD) patients excrete proteinuria, have low-protein diet, and receive glucocorticoid therapy. No one has evaluated the most influential factors on SAC in CKD patients. METHODS: A retrospective study. Hospitalized CKD patients with less than 1 g/gCreatinine proteinuria receiving glucocorticoid therapy (n=28), with 1 or more g/gCreatinine proteinuria not receiving glucocorticoid therapy (n=36), and with 1 or more g/gCreatinine proteinuria receiving glucocorticoid therapy (n=39) were enrolled. SAC, hemoglobin, proteinuria and blood pressure at the last outpatient check-up before hospitalization, on the second day of hospitalization, at the last laboratory examination before discharge, as well as at the first outpatient follow-up after discharge were analyzed. RESULTS: SAC decreased on the second day of hospitalization and increased at the first outpatient follow-up significantly in all groups. Unexpectedly, the change of SAC was irrelevant to the amount of proteinuria. CONCLUSIONS: SAC was affected by not only proteinuria, but also postural change, physical activity, and food in CKD patients. SAC should be analyzed by standardizing a patient's condition during phlebotomy. J. Med. Invest. 64: 146-152, February, 2017.

Re-recognition of Age-dependent Reference Range for the Serum Creatinine Level in Teenagers - A Case of Slowly Progressive Tubulointerstitial Nephritis which Occurred in an Adolescent.

For the first time, a 15-year-old boy was found to have a slight degree of proteinuria and microscopic hematuria during annual school urinalysis screening. His kidney function had already severely deteriorated. A kidney biopsy revealed tubulointerstitial nephritis (TIN) with diffuse inflammatory cell infiltration. His medical records showed his serum creatinine level to be 0.98 mg/dL two years ago, which was abnormally high considering his age. Although the etiology of slowly progressive TIN was unclear, glucocorticoid and immunosuppressant therapy improved his kidney function. This case report suggests that all doctors should recognize the reference range for the serum creatinine level in teenagers.