Acute tubulointerstitial nephritis in children- a retrospective case series in a UK tertiary paediatric centre

An updated approach to the evaluation of the urinary sediment

Examination of the urinary sediment (U-sed) is an important non-invasive, rapid, and inexpensive tool for the diagnosis and surveillance over time of renal diseases. In this Educational Review, we describe first how to collect, prepare, and examine urine samples in order to obtain reliable results. Then, we describe the U-sed findings in isolated microscopic hematuria, glomerular diseases, acute interstitial nephritis, acute kidney injury, reactivation of the BK virus in kidney transplant recipients, and crystalluric genetic diseases.

Clinical outcomes in paediatric tubulointerstitial nephritis and uveitis syndrome (TINU)

PURPOSE

To evaluate the clinical presentation, course, and outcomes of uveitis in paediatric patients with tubulointerstitial nephritis and uveitis syndrome (TINU).

METHODS

Multicentric Retrospective Cohort Study 110 patients ≤21 years of age diagnosed with TINU from 10 sites across the United States and Canada. Clinical diagnosis of TINU required uveitis diagnosed by an ophthalmologist, elevated serum creatinine (SCr) and elevated urine β2-microglobulin (β2M) or abnormal urinalysis. Renal biopsy and systemic illness were not mandatory. Univariate and multivariate analysis was performed to analyse risk factors and treatment modalities.

RESULTS

Median age was 13 years (Range (5.9-18.4); 52% male); median follow-up, 1.6 years (IQR 0.98-4.02). Uveitis was symptomatic in 90%, with bilateral anterior uveitis in 94%. Ninety-two (84%) patients required immunomodulatory treatment (IMT). Methotrexate (n = 44) and mycophenolate mofetil (n = 39) were the first agents after oral corticosteroids. 45% required addition of biologic agents (Adalimumab [n = 33], Infliximab [n = 8]). Younger age (p = 0.018), male sex (p = 0.011), and higher uveitis grade at presentation (p = 0.031) were associated with greater IMT ( ≥ 2) requirement. 53% had uveitis recurrence compared to 16% with nephritis recurrence. At the most recent visit, nephritis was controlled in 90%, while uveitis in 74%. Four (4%) patients required glaucoma surgery. Nine (8%) patients had renal complications.

CONCLUSIONS

Most patients with TINU require steroid-sparing IMT for control of uveitis, with nearly half requiring addition of biologic agents. Urinalysis, urine β2M and SCr testing should be considered in children presenting with uveitis, especially when the disease is bilateral and anterior.

New-Onset Acute Interstitial Nephritis Post-SARS-CoV-2 Infection and COVID-19 Vaccination: A Panoramic Review

The 2019 coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) has posed a considerable challenge to global healthcare. Acute interstitial nephritis (AIN) post SARS-CoV-2 infection and vaccination has been reported, but its clinical features and pathogenesis remained unclear. We reviewed so far the largest 22 cases of AIN post SARS-CoV-2 infection and 36 cases of AIN following COVID-19 vaccination. The onset of AIN was mainly related to messenger RNA vaccines (52.8%). Apart from fever, proteinuria (45.5%) was the main manifestation of AIN post SARS-CoV-2 infection, left acute kidney injury (AKI, 63.9%) in patients post COVID-19 vaccination. The potential mechanism of vaccination induced AIN was conjugating vaccines with proteins to form a hapten, which activated dendritic cells and promoted a cascade immunological reaction leading to AIN.

Clinical significance of kidney immune complex deposition in children with acute interstitial nephritis disease

BACKGROUND

Acute interstitial nephritis (AIN) is a relatively rare cause of acute kidney injury (AKI) in children. Immune complex (IC) deposition was rare in renal pathology of AIN.

METHODS

Based on the status and position of IC deposition, a total of 78 children with AIN were divided into two groups: the non-IC group and IC group. IC group was further divided into two subgroups: intraglomerular (IG)-IC group and extraglomerular (EG)-IC group. To compare the clinical and histological features, renal outcomes between groups.

RESULTS

The IC deposition, IG-IC and EG-IC deposition were observed in 22 (28.21%), 12 (15.38%) and 10 (12.82%) children, respectively. The IC group demonstrated a higher frequency of AKI, higher level of Scr, urine N-acetyl-β-D-glucosidase (NAG) enzyme, retinol-binding protein (RBP), neutrophil gelatinase-associated lipocalin (NGAL), higher frequency of neutrophils, plasma cells and eosinophils infiltrate, higher scores of interstitial inflammation (i), total inflammation (ti) and interstitial edema, lower level of estimated glomerular filtration rate (eGFR) as compared to non-IC group (p < 0.05, p < 0.01). EG-IC deposition positively moderate correlated with levels of RBP, IG-IC deposition positively moderate correlated with plasma cell infiltrate, interstitial inflammation (i), total inflammation (ti) and interstitial edema. Interstitial inflammation, EG-IC deposition and interstitial edema were risk factors for AKD in AIN, and interstitial fibrosis/tubular atrophy (IF/TA) was a risk factor for CKD in children with AIN.

CONCLUSION

IG-IC and EG-IC deposition positively correlated with severe clinical manifestations, glomerular and tubular injuries, and EG-IC deposition was risk factor for the progression of AIN in children.

Tubulointerstitial nephritis and uveitis in children during the COVID-19 pandemic: report of four cases

Tubulointerstitial nephritis and uveitis (TINU) is a rare autoimmune disorder often triggered by drugs and infections. Since the onset of the COVID-19 pandemic, we have observed an unusual cluster of paediatric cases. Four children (3 females) were diagnosed with TINU (median age 13 years) following a kidney biopsy and ophthalmologic assessment. Presenting symptoms included abdominal pain (3 cases), fatigue, weight loss and vomiting (2 cases). At presentation, median eGFR was 50.3 ml/min/1.73m2 (range 19.2-69.3). Anaemia was common (3 cases) with median haemoglobin of 10.45 g/dL (range 8.4-12.1). Two patients were hypokalaemic and 3 had non-hyperglycaemic glycosuria. Median urine protein:creatinine ratio was 117 mg/mmol (range 68-167). SARS-CoV-2 antibodies were detected in 3 cases at presentation. All were asymptomatic for COVID-19 with a negative PCR. Kidney function improved following high-dose steroids. However, disease relapse was observed during steroid tapering (2 cases) and upon discontinuation (2 cases). All patients responded well to further high dose steroids. Mycophenolate mofetil was introduced as a steroid-sparing agent. At latest follow up (range 11-16 months), median eGFR was 109.8 ml/min/1.73m2. All four patients continue on mycophenolate mofetil, with 2 patients applying topical steroids for uveitis. Our data suggest that SARS-CoV-2 infection might be a trigger for TINU.

Clinical Characteristics of Children With Acute Tubulointerstitial Nephritis: A Single-Center Experience

OBJECTIVE

Acute tubulointerstitial nephritis (ATIN) is an infiltration of the kidney interstitium with inflammatory cells. Medications are most frequently blamed for the etiology. Patients may present with non-specific signs and symptoms. Therefore, the diagnosis of ATIN is often delayed. In this study, clinical characteristics, treatment protocols, and outcomes of children diagnosed with ATIN were presented.

METHODS

This is a retrospective study based on the data of 18 patients diagnosed with ATIN between 2017 and 2022 at Gazi University. Patients were divided into two groups: steroid-treated (n=13) and non-steroid-treated (n=5). Clinical features and laboratory evaluations were compared between the groups.

RESULTS

The mean age of the patients was 14.4±2.6 years, and the great majority were girls (88.9%, n=16). ATIN was mostly medication-related (n=17, 94.4%). Steroids were started in one-third of patients using non-steroidal anti-inflammatory drugs. Steroids were started in 45.4% of the patients with eosinophilia, 75% of those with pyuria, 66.6% of those with hematuria, and half of the patients with increased kidney echogenicity. The kidney functions returned to normal ranges in all patients. In steroid-treated patients, although recovery times for serum creatinine were longer (7.2±2.5 vs. 71.2±100.7 days), blood eosinophil count reached normal values more rapidly (5.4±2.3 vs. 3.1±1.0 days).

CONCLUSION

ATIN can be associated with diverse clinical presentations. The first and most important step of treatment is to discontinue the medication responsible for the etiology. Steroid treatment improves eosinophilia more rapidly. However, randomized controlled studies are needed to determine further treatment steps and establish a more definite treatment protocol.

Renal outcomes in tubulointerstitial nephritis and uveitis (TINU) syndrome: a systematic review and meta-analysis

BACKGROUND

Tubulointerstitial nephritis and uveitis syndrome (TINU) is a rare condition characterised by bilateral uveitis and interstitial nephritis. There is no nationally, or internationally agreed upon treatment regimen. A systematic review was undertaken to report the renal outcomes in TINU, and treatments used.

METHODS

Medline (1969-2021) and EMBASE (1988-2021) databases were searched for primary studies, clinical practice guidelines and case reports of adult and paediatric TINU cases, as defined by Mandeville criteria. Two reviewers identified articles meeting inclusion criteria (registered with PROSPERO). Data were extracted into a synthesis table and meta-analysis performed. Quality of case series was also assessed.

RESULTS

One hundred twenty-two articles were identified, totalling 257 cases included in the meta-analysis. Females were more commonly affected than males (2:1), and median age was 19 years. GFR at follow-up correlated with nadir GFR, and the proportion with GFR <90 ml/min/1.73 m² was statistically different between adult and paediatric groups. Of the entire cohort, 40% had GFR <90 ml/min/1.73 m² at follow-up. Glucocorticoid monotherapy was the most common treatment (70%); other strategies included no treatment (9%) and immunosuppressant drugs (e.g. azathioprine), mostly in steroid-resistant cases, or as 'steroid-sparing' alternatives.

CONCLUSIONS

The majority of literature regarding TINU is limited to case reports and case series. There are no prospective trials assessing the effects of different treatments on renal outcomes, and currently employed treatment strategies are physician-specific without a reliable evidence-base. Prospective data collection as part of multicentre trials should be a research focus to improve the evidence-base.

Acute Interstitial Nephritis in the Pediatric Population: A Review of Etiologic Associations, Histologic Findings, and Clinical Outcome

BACKGROUND

Acute interstitial nephritis (AIN) is an infrequent cause of acute kidney injury in the pediatric population with a broad range of etiologies. This retrospective review attempts to characterize AIN in the pediatric population, delineate etiologic factors, histologic features, and clinical outcome.

MATERIALS AND METHODS

Institutional pathology reports were queried for a diagnosis of AIN between 1/2010 and 10/2021. Archived slides and reports and clinical records were reviewed.

RESULTS

Twenty-four patients were identified whose ages ranged from 5 to 20 years. A 8 cases (37.5%) were characterized as tubulointerstitial nephritis and uveitis (TINU), 4 cases (16.7%) were associated with an autoimmune disease, 4 cases (16.7%) were likely drug induced, and 8 cases (37.5%) had unclear etiology.

DISCUSSION

Although all cases of drug induced interstitial nephritis contained eosinophils they were not exclusive to drug induced interstitial nephritis. A prominent plasma cell infiltrate was seen in both cases of Sjögren's associated interstitial nephritis. The vast majority (n = 18, 75%) showed an improved serum creatinine (<1 mg/dL) 1 year post diagnosis/at last follow-up. In this pediatric series of AIN, TINU contributed to a large subset of cases with known etiologies. On follow up, majority of the cases demonstrated recovery of renal function.

Extracellular DNA concentrations in various aetiologies of acute kidney injury

Extracellular DNA (ecDNA) in plasma is a non-specific biomarker of tissue damage. Urinary ecDNA, especially of mitochondrial origin, is a potential non-invasive biomarker of kidney damage. Despite prominent tissue damage, ecDNA has not yet been comprehensively analysed in acute kidney injury (AKI). We analysed different fractions of ecDNA, i.e. total, nuclear and mitochondrial, in plasma and urine of children, and different animal models of AKI. We also analysed the activity of the deoxyribonuclease (DNase), which is contributes to the degradation of ecDNA. Patients with AKI had higher total and nuclear ecDNA in both, plasma and urine (sixfold and 12-fold in plasma, and 800-fold in urine, respectively), with no difference in mitochondrial ecDNA. This was mainly found for patients with AKI due to tubulointerstitial nephritis and atypical haemolytic uremic syndrome. Increased plasma ecDNA was also found in animal models of AKI, including adenine nephropathy (fivefold), haemolytic uremic syndrome (fourfold), and ischemia–reperfusion injury (1.5-fold). Total urinary ecDNA was higher in adenine nephropathy and ischemia–reperfusion injury (1300-fold and twofold, respectively). DNase activity in urine was significantly lower in all animal models of AKI in comparison to controls. In conclusion, plasma total and nuclear ecDNA and urinary total ecDNA is increased in patients and animals with particular entities of AKI, suggesting a mechanism-dependent release of ecDNA during AKI. Further studies should focus on the dynamics of ecDNA and its potential role in the pathogenesis of AKI.

Tubulointerstitial nephritis and uveitis syndrome in an adolescent female: a case report

BACKGROUND

Tubulointerstitial nephritis with uveitis syndrome is a rare disease affecting mainly children and young women. Tubulointerstitial nephritis with uveitis is a diagnosis of exclusion, requiring a high degree of clinical suspicion. Studies report recent infections or certain drugs as precipitating factors of a lymphocytic oculorenal immune response. The prognosis is usually favorable with topical and systemic corticosteroid therapy.

CASE PRESENTATION

We report a literature review and the case of a 14-year-old white girl, who presented to the ophthalmology department with features of one-sided uveitis. Upon transfer of patient to nephrological care, diagnostic work-up revealed renal involvement. Renal biopsy showed a mixed-cell and granulomatous tubulointerstitial nephritis with some noncaseating granulomas, leading to a diagnosis of tubulointerstitial nephritis with uveitis syndrome. With topical ocular and systemic corticosteroid therapy, the patients' condition improved over several weeks.

CONCLUSIONS

Our case highlights the importance of early recognition and treatment of this syndrome, where cross-specialty care typically leads to a favorable outcome.

Non-diabetic glycosuria as a diagnostic clue for acute tubulointerstitial nephritis in patients with azotemia

Background

Glycosuria is one of the manifestations of acute tubulointerstitial nephritis (ATIN), but may also be observed in other renal diseases. In this study, we investigated the value of non-diabetic glycosuria as a diagnostic clue for ATIN.

Methods

We retrospectively reviewed the medical records of adult patients who underwent a kidney biopsy as an evaluation for serum creatinine > 1.4 mg/dL. Patients with proteinuria in the nephrotic range, diabetes mellitus, or transplanted kidney were excluded. The laboratory abnormalities suggestive of tubular injury were compared between 28 patients (14 men and 14 women, mean age 48.5 ± 14.1 years) with ATIN and 116 patients (76 men and 40 women, mean age 53.1 ± 15.0 years) with other diagnoses.

Results

In ATIN, glycosuria (≥ 1+ on dipstick; 68%) was more frequent than hypophosphatemia (18%), hypouricemia (18%), hypokalemia (18%), and tubular proteinuria (40%). In other diagnoses, glycosuria (≥ 1+) was detected in 7 (6%) patients; 6 of them had the histological diagnosis of antineutrophil cytoplasmic antibody-associated glomerulonephritis. The presence of glycosuria (≥ 1+) had 68% sensitivity and 94% specificity for ATIN, with the positive likelihood ratio of 11.24 and the negative likelihood ratio of 0.34. Pyuria and low total CO₂ were equally and more sensitive (68% and 71%, respectively) than glycosuria (≥ 1+), but had no diagnostic value due to low specificities (58% and 60%, respectively).

Conclusion

In non-diabetic, non-nephrotic patients undergoing a kidney biopsy for azotemia, 1+ or higher glycosuria, if present, was a good predictor of the diagnosis of ATIN.

Long-term outcome of biopsy-proven idiopathic tubulointersitial nephritis with or without uveitis in children-a nationwide follow-up study

BACKGROUND

Only a few studies reporting the long-term outcome of children with idiopathic tubulointerstitial nephritis (TIN) and uveitis syndrome (TINU) are available. We studied the long-term kidney and ocular outcome in a nationwide cohort of children with TIN or TINU.

METHODS

All patients followed up for a minimum of 1 year by a paediatrician and an ophthalmologist were enrolled. The data on plasma creatinine (P-Cr), estimated glomerular filtration rate (eGFR), proteinuria, hypertension and uveitis were collected retrospectively.

RESULTS

Fifty-two patients were studied. Median age at time of diagnosis was 13.1 (1.8-16.9) years and median follow-up time was 5.7 (1.1-21.2) years. Forty-five (87%) patients were initially treated with glucocorticoids. The median of the maximum P-Cr was 162 μmol/l (47-1,016) and that of eGFR 47 ml/min/1.73m² (8-124). Uveitis was diagnosed in 33 patients (63%) and 21 (40%) patients developed chronic uveitis. P-Cr normalised in a median of 2 months. Eleven (21%) patients had nephritis recurrence during or after discontinuation of glucocorticoids. At the latest follow-up, 13 (25%) patients had eGFR < 90 ml/min/1.73m² (median 83; 61-89 ml/min/1.73m²). Six patients had tubular proteinuria; all presented with TIN without uveitis. Seven (13%) patients were hypertensive. Eleven (21%) patients had uveitis. One patient developed uraemia and was later transplanted.

CONCLUSIONS

Our study questions the previously reported good long-term kidney and ocular outcome of patients with TIN/TINU. Decreased kidney function and/or ocular co-morbidities may persist for several years; thus, both kidney and ocular follow-up for at least 1 year is warranted. A higher resolution version of the Graphical abstract is available as Supplementary information.