Kidney Week

Abstract: SA-PO0961

Long-Term Clinical Course in Tubulointerstitial Nephritis with IgM-Positive Plasma Cells (IgMPC-TIN): A Case Series of Five Patients

Session Information

• Pathology: Updates and Insights
  November 08, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Pathology and Lab Medicine

• 1800 Pathology and Lab Medicine

Authors

• Takahashi, Naoki, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Naoki Takahashi, MD, PhD

• Yoshida, Haruyoshi, Koritsu Obama Byoin Kumiai, Obama, Fukui Prefecture, Japan

Haruyoshi Yoshida, MD, PhD

• Kimura, Hideki, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Hideki Kimura, MD, PhD

• Iwamura, Nanami, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Nanami Iwamura, MD, PhD

• Nishikawa, Sho, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Sho Nishikawa, MD

• Nishimori, Kazuhisa, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Kazuhisa Nishimori, MD

• Fukushima, Sachiko, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Sachiko Fukushima, MD

• Nishikawa, Yudai, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Yudai Nishikawa, MD

• Kobayashi, Mamiko, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Mamiko Kobayashi, MD

• Kasuno, Kenji, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Kenji Kasuno, MD, PhD

• Iwano, Masayuki, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Masayuki Iwano, MD, PhD

• Toyama, Tadashi, Fukui Daigaku Igakubu, Yoshida District, Fukui Prefecture, Japan

Tadashi Toyama, MD, PhD

Background

IgMPC-TIN is a recently recognized subtype of tubulointerstitial nephritis characterized by abundant interstitial IgM-positive plasma cells, elevated serum IgM, distal renal tubular acidosis, and Fanconi syndrome, often associated with primary biliary cholangitis (PBC). However, the long-term treatment outcomes remain poorly described.

Methods

We retrospectively analyzed five female patients with IgMPC-TIN who were followed-up for 3–17 years. The eGFR slopes were calculated using the regression of serial measurements and expressed as ΔeGFR. The treatment course was divided into two phases: early (0–7 months) and chronic (> 7 months).

Results

At diagnosis, the mean age was 50.2 ± 10.8 years; mean serum IgM 833 ± 257 mg/dL, eGFR 43.9 ± 13.3 mL/min/1.73 m², and urinary β₂-microglobulin 46,331 ± 28,148 μg/L. Four patients had PBC, and one had elevated γ-glutamyltransferase levels, suggesting cholestatic liver injury. All patients received ursodeoxycholic acid. Three patients were treated with glucocorticoids (glucocorticoid group: patients 1, 3, and 5), two of whom also received immunosuppressants. In the glucocorticoid group, ΔeGFR improved markedly in the early phase, with peaks of +6.5, +3.7, and +2.1 mL/min/1.73 m²/month in patients 1, 3, and 5, respectively, but declined to near zero by the end of chronic phase. Among those without glucocorticoids, patient 2 showed an initial decline in ΔeGFR (-6.2 mL/min/1.73 m²/month), which improved to -0.6 mL/min/1.73 m²/month by the end of the early phase, while patient 4 remained near zero throughout. In the chronic phase, ΔeGFR were -1.4, -3.0, and +0.7 mL/min/1.73 m²/year in patients 1, 3, and 5, and -0.8 and -0.4 in patients 2 and 4. Notably, four patients developed urinary tract stones, three of whom showed an increased stone burden. Patient 3 had two episodes of hydronephrosis due to ureteral stones, which likely contributed to the most severe chronic eGFR decline.

Conclusion

The long-term eGFR decline in IgMPC-TIN may be mild in the absence of hydronephrosis, without an apparent effect of glucocorticoids. These findings highlight the importance of optimizing long-term treatment and preventing urolithiasis in order to preserve renal function.

Funding

• Government Support – Non-U.S.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025z13bybzk