PMC8105656_01
FDG PET whole body maximum intensity projection (A) and fused PET and CT coronal views of the left shoulder (B) and hip (C) demonstrating diffuse, symmetric, periarticular inflammatory uptake in the shoulders, wrists, hips and knees.
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However, a diffuse symmetric large joint polyarthropathy was identified, with SUVmax of 7.0 at the right hip (Fig. 1).
Cytospin preparation of synovial fluid showing Congo red-positive material (A) demonstrating apple-green birefringence under polarized light (B). Both images Congo red stain, 400x. (C) Proteomic detection of ATTR in amyloid deposits from the synovial fluid cell block. Within the boxes, the numbers represent the total number of spectra matched to the listed protein and the colors indicate the probability that the spectra represent the identified protein (only spectra with > 95% probability of a match to an identified protein [green boxes] are considered for diagnostic interpretation). There are abundant spectra for the universal amyloid proteins (APOE, SAP, and APOAIV; blue and yellow stars), providing biochemical evidence that amyloid is present in the microdissected sample. There are also many spectra corresponding to transthyretin. The somewhat elevated spectral counts for immunoglobulin lambda and immunoglobulin gamma as well as for serum albumin and fibrinogen (serum-related proteins) indicate concomitant serum contamination by the patient's known IgG-lambda myeloma (we thank Jason Theis for providing the mass spectrometry scaffold image).
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A cytospins preparation of the synovial fluid was stained with CR, showing rare small fragments of CR-positive, acellular proteinaceous material showing classical apple- green birefringence under polarized light (Fig. 2A-B). A liquid chromatography tandem mass spectrometry analysis of the deposits detected a peptide profile consistent with TTR-type amyloid deposition (Fig. 2C)., with no amino acid sequence abnormality in the transthyretin protein, consistent with wild-type TTR.