Extending Amyloidosis Diagnosis: A Rare Case of Peritoneal AL Amyloidosis Revealed by 18 F-FDG PET/CT and 99m Tc-PYP SPECT/CT.

We present a case with systemic amyloidosis secondary to immunoglobulin light-chain amyloidosis (AL amyloidosis), which 18 F-FDG PET/CT and 99m Tc-PYP scintigraphy revealed amyloid deposition in the peritoneum, omentum, and mesentery. AL amyloidosis is characterized by the proliferation of clonal plasma cells and increased production and extracellular accumulation of immunoglobulin light chains, leading to organ malfunction. Even though AL amyloidosis can affect the gastrointestinal system, peritoneal involvement is rarely observed. PET/CT and SPECT/CT images showed moderate to slightly increased tracer uptake in affected organs.