Kidney Week

Abstract: SA-PO0724

Caught in the Complement Cascade: A Challenging Case of C1q Nephropathy

Session Information

• Glomerular Diseases: Complement-Mediated Glomerulopathies and Infection-Related GN
  October 24, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1402 Glomerular Diseases: Clinical, Outcomes, and Therapeutics

Authors

• Henze, Alexander Otto, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

Alexander Otto Henze, MD

• Arefin, Mohammed Ahnaf, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

Mohammed Ahnaf Arefin, MD

• Amer, Imran, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

Imran Amer, MD

• Kanduri, Swetha Rani, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

Swetha Rani Kanduri, MD, MBBS, FASN

• Ryan, Eric, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States

Eric Ryan, MD

Introduction

C1q nephropathy is a rare glomerular disease defined by mesangial C1q deposition on immunofluorescence microscopy without systemic lupus erythematosus. The pathogenesis is poorly understood but involves dysregulation of complement component, C1q, which normally binds immune complexes and activates the classical pathway. Clinical presentations vary from asymptomatic proteinuria to rapidly progressive glomerulonephritis. Patients often become dependent on systemic steroids for control, making management complicated. Here, we present a case of C1q nephropathy complicated by recurrences and limited treatment options.

Case Description

Our patient is a 19-year-old male who presented in 2020 with biopsy-proven C1q nephropathy. He was previously diagnosed in India with idiopathic nephrotic syndrome requiring repeat steroid courses. He immigrated to the US and experienced relapses every 6-8 months requiring steroids, levamisole, and cyclophosphamide. In 2017, he received a renal biopsy. Immunofluorescence demonstrated mesangium staining positive for C1q and lambda light chain, with electron microscopy noting subtotal effacement of foot processes. Following the biopsy, he was started on tacrolimus and prednisone with improvement until January 2022. He has since experienced 10 relapses, frequently triggered by upper respiratory infection. He develops nephrotic-range proteinuria, with UPCR ranging from 4.2 gm/gm to undetectably high. He has never required renal replacement therapy with maximum creatinine of 1.42 mg/dL. Each episode was treated with tapered high-dose steroids, with complete resolution of proteinuria. With the temporal trend of relapses and high-dose steroid therapy, our patient demonstrated a common finding of steroid dependence amongst C1q nephropathy patients.

Discussion

Management of C1q is challenging and not well-studied. Steroids can help, but long-term use confers well-established side effects. Taper periods between pulse doses also expose the patient to cumulative renal damage that can lead to earlier end-stage renal disease. Because this disease is uncommon and poorly understood, few alternative therapies have been described. Case reports have supported use of rituximab, but regimens varied and patients were not followed longitudinally. Other non-immunologic approaches to reducing proteinuria have also been explored, including enalapril, SGLT2 inhibitors, and mineralocorticoid receptor antagonists.