Idiopathic hypocomplementemic immune-complex-mediated tubulointerstitial nephritis

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: diagnosis, treatment, and monitoring

Tubulointerstitial nephritis (TIN) is a frequent cause of acute kidney injury (AKI) that can lead to chronic kidney disease (CKD). TIN is associated with an immune-mediated infiltration of the kidney interstitium by inflammatory cells, which may progress to fibrosis. Patients often present with nonspecific symptoms, which can lead to delayed diagnosis and treatment of the disease. Etiology can be drug-induced, infectious, idiopathic, genetic, or related to a systemic inflammatory condition such as tubulointerstitial nephritis and uveitis (TINU) syndrome, inflammatory bowel disease, or immunoglobulin G4 (IgG4)-associated immune complex multiorgan autoimmune disease (MAD). It is imperative to have a high clinical suspicion for TIN in order to remove potential offending agents and treat any associated systemic diseases. Treatment is ultimately dependent on underlying etiology. While there are no randomized controlled clinical trials to assess treatment choice and efficacy in TIN, corticosteroids have been a mainstay of therapy, and recent studies have suggested a possible role for mycophenolate mofetil. Urinary biomarkers such as alpha1- and beta2-microglobulin may help diagnose and monitor disease activity in TIN. Screening for TIN should be implemented in children with inflammatory bowel disease, uveitis, or IgG4-associated MAD.

Diagnosis of IgG4-related tubulointerstitial nephritis

IgG4-related systemic disease is an autoimmune disease that was first recognized in the pancreas but also affects other organs. This disease may manifest as tubulointerstitial nephritis (IgG4-TIN), but its clinicopathologic features in the kidney are not well described. Of the 35 patients with IgG4-TIN whose renal tissue specimens we examined, 27 (77%) had acute or progressive chronic renal failure, 29 (83%) had involvement of other organ systems, and 18 of 23 (78%) had radiographic abnormalities. Elevated total IgG or IgG4 serum levels were present in 79%. All pathologic specimens featured plasma cell-rich TIN, with most showing diffuse, expansile interstitial fibrosis. Immune complexes along the tubular basement membranes were present in 25 of 30 (83%). All specimens had a moderate to marked increase in IgG4+ plasma cells by immunohistochemistry. We used a control group of 175 pathologic specimens with plasma cell-rich interstitial infiltrates that can mimic IgG4-TIN to examine the diagnostic utility of IgG4 immunostaining. Excluding pauci-immune necrotizing and crescentic glomerulonephritis, IgG4 immunohistochemistry had a sensitivity of 100% (95% CI 90-100%) and a specificity of 92% (95% CI 86-95%) for IgG4-TIN. Of the 19 patients with renal failure for whom treatment and follow-up data were available, 17 (89%) responded to prednisone. In summary, because no single test definitively diagnoses IgG4-related systemic disease, we rely on a combination of histologic, immunophenotypic, clinical, radiographic, and laboratory features. When the disease manifests in the kidney, our data support diagnostic criteria that can distinguish IgG4-TIN from other types of TIN.

Hypocomplementaemic immune complex tubulointerstitial nephritis

We report a rare cause of rapidly progressive renal failure associated with low complement, positive ANA but negative anti DS-DNA. A renal biopsy demonstrated tubulointerstitial nephritis with positive immunoglobulin staining involving the interstitium and tubular basement membrane but glomerular sparing. A review of the literature and differential diagnosis are discussed.