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E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
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Abstract titles should be brief and reflect the content of the abstract.
IgG4-related disease (IgG4RD) is a rare but clinically significant systemic fibroinflammatory disorder characterized by IgG4 plasma cell infiltration and tissue fibrosis, with an estimated prevalence of 5.3 per 100,000 persons in the United States. The kidney is one of the major target organs, affected in 7%–30% of patients. The US FDA has recently approved inebilizumab as the first and only therapy for adults with IgG4RD.
A 63-year-old man with multiple comorbidities, including obesity, hypertension, prediabetes, hyperlipidemia, and fatty liver disease, was referred for worsening of baseline kidney function. One year prior, he underwent submandibular salivary gland excision for a mass; however, the pathology ruled out malignancy. Over the following months, he developed unexplained weight loss and systemic lymphadenopathy. CT scan revealed subpleural lung nodules, bilateral iliac and retroperitoneal lymphadenopathy, and two complex right kidney cysts. Despite hypermetabolic lymph nodes concerning for lymphoma on PET scan, lymph node biopsy revealed nonspecific polymorphous lymphocytes without malignancy.
His baseline creatinine (Cr) was 1.24 mg/dL, UPCR 190 mg/g, UACR 48 mg/g, and HbA1c 5.7%, which increased at presentation to 2.67 mg/dL, 313 mg/g, 112 mg/g, and 6.2%, respectively. Serologic workup was negative for ANA, ANCA, SSA, SSB, SPEP/UPEP, and Quantiferon-TB Gold but notable for low complement (C3 57 mg/dL, C4 3 mg/dL) and elevated IgG4 (968 mg/dL). Kidney biopsy demonstrated diffuse IgG4-positive plasma cell–rich tubulointerstitial inflammation with storiform fibrosis and granular IgG deposits in the tubular basement membrane, mesangium, and Bowman’s capsule. A diagnosis of IgG4-related tubulointerstitial nephritis (TIN) was established.
The patient was started on prednisone 30 mg daily for 4 weeks, resulting in an improvement in kidney function (Cr 1.4 mg/dL), normalization of complement and IgG4 levels, and resolution of lymphadenopathy. Prednisone was tapered over 3 months and discontinued. Several months later, he experienced a disease flare with rising Cr, fatigue, decreased C3, and elevated IgG4 levels. Given his preference to avoid steroids, he was initiated on inebilizumab monotherapy. He received two 300-mg intravenous infusions on days 1 and 15, with a planned maintenance dose at week 26.
Following treatment, IgG4 levels progressively declined (from 523 to 215 mg/dL), with stabilization of kidney function (Cr 1.62 mg/dL, eGFR 47 mL/min/1.73m²) and normalization of C3 levels. He remains off steroids with an improved metabolic profile and no recurrence of lymphadenopathy, demonstrating a favorable early response to inebilizumab.
While glucocorticoids have historically been used as the first-line therapy for IgG4RD, relapse after tapering is common, creating a significant need for durable, steroid-sparing treatment. The recent FDA approval of inebilizumab, a CD19-targeted B-cell–depleting therapy, represents a substantial advancement in managing IgG4RD.
Our case illustrates a favorable response to inebilizumab monotherapy in a patient with IgG4-related TIN who experienced a disease flare following glucocorticoid discontinuation and opted to avoid further steroid use. These findings align with MITIGATE trial data and support the use of inebilizumab as an effective therapy for IgG4RD with kidney involvement.
