Accurate typing of amyloid is mandatory because the treatment modalities of various types of amyloid are very different. Renal amyloidosis can at times be easy to classify into AL and AA types depending on immunofluorescence and immunohistochemistry studies. Technically, AL amyloidosis or AH amyloidosis are plasma cell diseases and either light chain or heavy chain disorder that have one chain predominance on IF and then subtypes using staining for AL or AH. AA amyloidosis is usually secondary to chronic illness such as RA, FMF, Infections, sometimes malignancies like renal cell and Hodgkin's Lymphoma.
A novel technique has come into light in helping diagnosis Amyloidosis. It is the LMD/MS technique or Laser micro dissection combined with mass spectrometry. From the Mayo Clinic, using this technique, they were able to diagnosis even rare cases that might not have been picked up on regular staining via AA or AL and perhaps even medullary Amyloidosis. They showed that LMD/MS is a useful and sensitive technique for the diagnosis of amyloid and for accurate typing of the amyloidosis, particularly problematic cases of amyloid. To show the usefulness of LMD/MS in typing renal amyloidosis, they demonstrate four cases of renal amyloidosis that were diagnostically challenging. What is this method?
About 10-μm-thick sections of formalin-fixed paraffin-embedded tissues were stained with Congo red. Glomeruli with positive Congo red areas viewed under a fluorescence light source appeared bright red. The Congo red deposits were identified under fluorescence light and microdissected with LMD. The microdissected material was collected analyzed by liquid chromatography electrospray tandem mass spect. The MS result value indicates the total number of mass spectrum collected on the mass spectrometer and matched to the protein using the proteomic software. A higher number of mass spectra is indicative of greater abundance and will typically yield greater amino acid sequence coverage.
Thus specific proteins were identified and diagnosis was made
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