Spectrum of IgG4-related Kidney Disease at a Tertiary Care Center

IgG4-related kidney disease (IgG4 RKD) is increasingly reported with varied manifestations. The present study was carried out to study the spectrum of IgG4 RKD. All patients with renal manifestation associated with conditions known to be associated with IgG4-related diseases (IgG4 RDs), or renal imaging or histology suggestive of IgG4 RKD were included and evaluated further. Patients with known extrarenal IgG4RD were also screened for renal involvement. Out of 40 patients screened over a period of 15 months, IgG4 RKD was diagnosed in 8. Majority were male (87.5%) with mean age being 56 years. Disease spectrum ranged from normal renal function in one to renal failure requiring dialysis in another two patients. Significant proteinuria was uncommon (12.5%) while hematuria was not seen in any patient. Tubulointerstitial nephritis was seen in all four patients who underwent kidney biopsy. Two patients had associated glomerular lesions in the form of immune complex crescentic glomerulonephritis. The most common imaging abnormality was hypodense renal lesions seen in 2 patients. Elevated IgG4 levels had 87.5% sensitivity and 78.3% specificity for IgG4 RKD and levels did not correlate with disease severity. Of 4 patients treated with steroids, 3 showed improvement in renal function. IgG4 RKD is an uncommon disease even at a referral tertiary care center. Elevated IgG4 levels alone are neither sensitive nor specific for the diagnosis of IgG4 RKD, and a combination of clinical, imaging, serological, and histological features are required for diagnosis.