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Abstract: FR-PO208

Localized Amyloidosis: The Great Masquerader

Session Information

Category: Onconephrology

  • 1600 Onconephrology

Authors

  • Balakrishnan, Suryanarayanan, Saint Vincent Hospital, Worcester, Massachusetts, United States
  • Prabhu, Sushmita, Saint Vincent Hospital, Worcester, Massachusetts, United States
  • Martin, Suzanne Gwen, Saint Vincent Hospital, Worcester, Massachusetts, United States
Introduction

Amyloidosis is characterized by misfolding of extracellular proteins and deposition in tissues as insoluble fibrils, causing end-organ damage. Localized amyloidosis (LA) without a plasma cell dyscrasia (AL amyloidosis) or chronic inflammation (AA amyloidosis) is rare. LA tends to involve the bladder, upper and lower respiratory tract, skin and eyes. LA presents as a tumor-like lesion, and patients may undergo extensive, and sometimes invasive, testing. LA of the bladder can present with painless hematuria, mimicking urologic malignancy.

Case Description

80M with Stage IIIA CKD, BPH, and atrial fibrillation on warfarin presented with intermittent gross hematuria over many years. Two cystoscopies in the last 5 years were negative for malignancy, with inflammation on biopsy. Labs were reassuring for stable hematocrit and baseline creatinine. Urine sediment revealed nondysmorphic RBCs. Urine protein:Cr ratio was 816mg/gCr. CT abd/pelvis showed diffuse circumferential thickening of the distal right ureter and nodular thickening of the right UVJ. Repeat cystoscopy showed the right ureteral orifice to be surrounded by erythema and thickening, concerning for a ureteral or atypical bladder mass. Biopsy showed chronic inflammation and amorphous, Congo red-positive material consistent with amyloidosis, and he underwent transuretheral resection. Immunofixation and serum free light chain ratio were negative for plasma cell dyscrasia. He had no manifestations of amyloidosis in other organs. Proteinuria and creatinine remain stable 8 years later, around 500mg/day and 1.1-1.3mg/dL, respectively.

Discussion

Localized bladder amyloidosis may masquerade as malignancy, often presenting with painless gross hematuria and/or lower urinary tract symptoms. Cystoscopy may raise concern for malignancy, and biopsy may only show nonspecific inflammation unless Congo red staining is performed. Securing the diagnosis of amyloidosis can prevent unnecessary procedures. Mass spectrometry is preferred to identify the causative misfolded protein. Primary bladder amyloidosis is rare and systemic amyloidosis must be excluded. If left untreated, localized bladder amyloidosis can lead to symptoms of obstructive uropathy. Treatment is aimed at transurethral excision of the lesion, and surveillance for recurrence is required. The prognosis is excellent, with only 1% progressing to systemic disease.