How is amyloidosis diagnosed?

Updated: May 09, 2019
  • Author: Robert O Holmes, Jr, DO; Chief Editor: Herbert S Diamond, MD  more...
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Amyloidosis is diagnosed when Congo red–binding material is demonstrated in a biopsy specimen. Because different types of amyloidosis require different approaches to treatment, determining only that a patient has a diagnosis of amyloidosis is no longer adequate. A clinical situation may suggest the type of amyloidosis, but the diagnosis generally must be confirmed by immunostaining a biopsy specimen. Antibodies against the major amyloid fibril precursors are commercially available. For example, AL, ATTR, and Aβ2 M can present as carpal tunnel syndrome or gastrointestinal amyloidosis, but each has a different etiology and requires a different treatment approach.

Similarly, determining whether the amyloid is of the AL or ATTR type is often difficult in patients with cardiac amyloidosis, because the clinical picture usually is similar. Without immunostaining to identify the type of deposited protein, an incorrect diagnosis can lead to ineffective and, perhaps, harmful treatment. Be wary of drawing diagnostic conclusions from indirect tests (eg, monoclonal serum proteins) because the results of these presumptive diagnostic tests can be misleading; for example, monoclonal serum immunoglobulins are common in patients older than 70 years, but the most common form of cardiac amyloidosis is derived from TTR.

New adjuncts to traditional laboratory testing are now available. The serum free light chain test is commercially available and can aid in screening, diagnosis, prognosis, and treatment monitoring by detecting low concentrations of free light chains and can measure the ratio of kappa chains to lambda chains. [79]

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