A case of IgG4-related kidney disease with predominantly unilateral renal atrophy

Abstract

A 73-year-old Japanese woman was diagnosed with type 1 autoimmune pancreatitis (AIP) without kidney lesions. She was treated with prednisolone (PSL) 30 mg/day, and her AIP symptoms promptly improved, after which the PSL dose was gradually tapered to 5 mg/day. Her renal function had remained normal (serum creatinine 0.7 mg/dL) until 1 year before the current admission without any imaging abnormalities in the kidney. However, during this past year her renal function gradually declined (serum creatinine 1.1 mg/dL). Follow-up computed tomography incidentally revealed unilateral renal atrophy, which rapidly progressed during the subsequent 10-month period without left kidney atrophy. A diagnosis of IgG4-RKD probably due to TIN was made, and we increased the dose of prednisolone to 30 mg/day. 1 month after administration, multiple low-density lesions on both kidneys were improved slightly but almost all lesions persisted as atrophic scars. Our case suggested that unilateral renal atrophy can develop in patients with IgG4-related tubulointerstitial nephritis without hydronephrosis caused by retroperitoneal fibrosis, and that monitoring the serum creatinine levels is not always sufficient, thereby highlighting the importance of regular imaging monitoring to detect newly developing kidney lesions.

IgG4-related kidney disease and retroperitoneal fibrosis: An update

“…In some cases, with IgG4-RD without renal involvement, renal parenchymal lesions newly developed as a recurrence of the disease during the maintenance steroid therapy [71]. Since kidney is one of the most frequently affected organs of this diseases, annual imaging follow-up is necessary even if kidney is not involved at the first diagnosis.…”

“…To detect recurrence or newly developed lesions in the kidney, NAG, and b2 microglobulin (b2MG) have been thought to be promising biomarkers [72]. However, previous reports showed that such urinary biomarkers are not necessarily elevated in IgG4-TIN patients [71]. In addition, Mizushima et al documented that urine NAG and b2MG concentrations fluctuate despite successful corticosteroid therapy [67].…”

Imaging findings of IgG4-related kidney disease without extrarenal organ involvement

“…[18,19] Renal pelvic lesions manifest as diffused wall thickening of the renal pelvis or soft-tissue mass encasing the pelvis, and the lesions exhibit similar intensity (on T2WI images) and enhancement pattern compared with parenchymal lesions. [13,14,17] Perinephric lesions are rare and appear as a rim-like lesion around the renal capsule, either diffuse or focal. [13,20] All 3 types of lesions of the kidneys can be unilateral or bilateral.…”