Negative Fat Pad Biopsy in Systemic AL: A Case Report Analyzing the Preferred Amyloidosis Screening Test

Light chain amyloidosis (AL) causes irreversible multi-organ damage if not diagnosed early in the disease process. Fat pad biopsy is thought to be a highly sensitive screening test in systemic AL cases, especially if greater than three organs are involved. We present a case of a 64-year-old female who was admitted to the hospital with worsening heart and kidney failure, anasarca, increased free serum lambda light chains, and a negative fat pad biopsy for amyloidosis. Later, she developed asystole, bradycardia, severe hypotension, and respiratory distress. Because X-rays of her calvarium showed multiple osteolytic lesions, a bone marrow biopsy was planned to assess for multiple myeloma. Due to her non-reassuring vitals, the biopsy was not attempted, and she passed away several weeks later. Autopsy findings identified the cause of death as multiple system organ failure due to systemic AL. Through microscopic examination, pathologists found amyloid deposits in her heart, kidneys, rectum, thyroid, adrenals, bone marrow, liver, and spleen. Postmortem fat pad biopsy was negative; however, bone marrow biopsy demonstrated clusters of CD138-positive cells, confirming plasma cell dyscrasia. In cases with a negative fat pad biopsy, an additional superficial or involved organ biopsy should be pursued to establish a diagnosis of amyloidosis if strong clinical suspicion exists.