discussion
Amyloidosis can be classified into systemic and localized, and can be classified according to the type of deposited fibrinogen into immunoglobulin light chain amyloidosis (AL), amyloid A amyloidosis (AA), β2 microglobulin amyloidosis (Aβ2M) and transthyretin amyloidosis (ATTR).(3) In systemic amyloidosis, the amyloid is deposited away from the site where it is produced, and it is transported via the circulatory system to the site of deposition. In localized amyloidosis, the location of amyloid production and deposition are the same. It is mainly caused by the AL amyloid, which is produced and deposited in local sites.(4) The exact etiology of localized amyloidosis is not yet known.
When amyloidosis is suspected, it requires tissue biopsy under local anesthesia and microscopic examination (using H&E and Congo red stains) are usually sufficient to establish a diagnosis. The next step is to exclude other organ involvements in systemic amyloidosis, then exclude underlying systemic disease (e.g. chronic inflammatory arthritis, tuberculosis, familial Mediterranean fever, Crohn’s disease…etc). Finally, it’s important to establish the subtype of amyloidosis; This is usually tested using serum or urine immunofixation electrophoresis to search for a clonal disorder.(5)