Kidney Week

Abstract: FR-PO1253

When Inflammation Overwhelms the Kidneys: Castleman Disease-Associated AKI and Secondary AA Amyloidosis

Session Information

• Onconephrology: Diagnostic Dilemmas, Therapy-Related Toxicities, and Clinical Cases
  October 23, 2026 | Location: Exhibit Hall A, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Onconephrology

• 1600 Onconephrology

Authors

• Pico-Ramirez, Alexandra C., Universidad de Puerto Rico Escuela de Medicina, San Juan, Puerto Rico

Alexandra C. Pico-Ramirez, MD

• Vazquez Morales, Emily, Universidad de Puerto Rico Escuela de Medicina, San Juan, Puerto Rico

Emily Vazquez Morales, MD

• Vega-Colon, Jesus Daniel, Universidad de Puerto Rico Escuela de Medicina, San Juan, Puerto Rico

Jesus Daniel Vega-Colon, MD

• Ocasio Melendez, Ileana E., Universidad de Puerto Rico Escuela de Medicina, San Juan, Puerto Rico

Ileana E. Ocasio Melendez, MD, FASN

Introduction

Castleman disease is a rare lymphoproliferative disorder characterized by lymph node enlargement, systemic inflammation, and cytokine dysregulation, most notably involving interleukin-6. Persistent inflammation may lead to secondary AA amyloidosis associated with multiorgan dysfunction. Renal involvement is uncommon but may manifest as proteinuria, nephrotic syndrome, thrombotic microangiopathy, or acute kidney injury (AKI) due to amyloid deposition.

Case Description

We report a 40-year-old male with intravenous drug use and hepatitis C infection who presented with progressive weight loss and generalized edema. Physical examination with significant lower extremity edema, and imaging with bulky retroperitoneal lymphadenopathy. Initial laboratories revealed normocytic normochromic anemia with preserved renal function. Excisional biopsy of an inguinal lymph node showed vascular transformation of lymph node sinuses, raising concern for Castleman disease. Shortly thereafter, the patient developed severe AKI with non-nephrotic range proteinuria of 1.9 g/g, anuria, uremia, and refractory volume overload requiring hemodialysis. Inflammatory markers were elevated, including IL-6 of 226.94 pg/mL, supporting a severe inflammatory state. Renal biopsy was considered; however, refractory shock and thrombocytopenia significantly increased procedural risk and precluded safe biopsy. During hospitalization, he developed hematochezia requiring colonoscopy. Biopsy of the sigmoid colon and rectum with Congo red staining demonstrated apple-green birefringence, confirming amyloid deposition and strongly supporting systemic AA amyloidosis. Steroids and rituximab were initiated, but the patient remained dialysis-dependent without hematologic improvement.

Discussion

This case highlights a rare and severe presentation of suspected Castleman disease complicated by systemic AA amyloidosis, causing irreversible dialysis-dependent AKI. The aggressive inflammatory phenotype can rapidly progress to multiorgan failure, emphasizing the importance of early recognition and prompt targeted therapy. In patients with unexplained systemic inflammation, lymphadenopathy, and renal dysfunction, Castleman disease with secondary AA amyloidosis should remain an important diagnostic consideration. When renal biopsy is not feasible, extra-renal tissue biopsy may provide sufficient diagnostic evidence.