Supplementary Material for: Urinary stricture due to localized urethral AL amyloidosis: a case report and literature review

The deposition of amyloid fibrils in various organs is a hallmark of amyloidosis, which is rarely isolated to a single site. We present a case of localized AL amyloidosis in a 23-year-old male who presented with hematuria from urethral stricture. Biopsy during urethroplasty confirmed amyloid deposition, and liquid chromatography-mass spectrometry identified the AL subtype. A comprehensive workup, including bone marrow biopsy, fat pad biopsy, cardiac workup and serum protein electrophoresis, excluded monoclonal disorder as well as widespread amyloid involvement. The patient underwent a two-stage urethroplasty and no evidence of recurrence locally or systemically during follow-up. This case emphasizes the importance of considering urethral amyloidosis in the differential diagnosis of urethral strictures, amyloid typing and workup to excluding systemic involvement. True localized AL amyloidosis does not need amyloid directed therapy initially but warrants close monitoring.