Diagnostic and therapeutic approach of systemic amyloidosis.

Amyloidosis is a group of diseases, all characterised by deposition of protein fibrils with a beta-sheet structure. This structure generates affinity of amyloid for Congo red dye and is resistant to proteolysis. Three types of systemic amyloidosis are important for the clinician: AA (related to underlying chronic inflammation), AL (related to underlying monoclonal light chain production) and ATTR amyloidosis (related to old age or underlying hereditary mutations of transthyretin). Signs and symptoms vary considerably among the three types and the choice of treatment differs completely. A stepwise approach in diagnosis and therapy is presented. When amyloidosis is suspected the first step is histological proof of amyloid and the second is proof of systemic involvement. The next two steps are determination of the type of amyloid followed by detection of the precursor protein. The fifth step is a thoughtful clinical evaluation, necessary for assessment of prognosis and therapy. Subsequently, the choice of therapy is based on the 'precursor-product' concept. In the final step, the effects of therapy on the underlying disease as well as on the amyloidosis are assessed during follow-up. In this evaluation serum amyloid P component (SAP) scintigraphy helps to show organ involvement and therapy response.