Systemic amyloidses are life threatening disorders which formerly were regarded as implacably deadly. However, there are nowadays a number of treatment options and more are under development. An early diagnosis is necessary.
The only way for a definite diagnosis is through a tissue biopsy. The most simple biopsy for systemic amyloidosis is that from subcutaneous adipose tissue over the abdomen. Sufficient material can be obtained with a needle that is not to thin. A punch biopsy including subcutaneous fat tissue or a small surgical biopsy are good alternatives. Preferably, the material should be sent to the laboratory as fresh, not fixated. Furthermore, it is no longer enough with a general diagnosis of amyloidosis; the biochemical nature has to be determined. The commonly used principle to find out the type of amyloid only by clinical parameters are unsafe. For example, AL amyloidosis may develop in an individual with a chronic inflammatory disease such as rheumatoid arthritis.
Instead, determination of the type of amyloid has to be performed directly on or from a tissue specimen. A number of different methods are used in clinical laboratories and mainly depend on personal experience.
• Immunohistochemistry. This is the most commonly used method for determination of amyloid type in pathology laboratories. It is, however, a method with definite limitations since it requires a long experience of amyloid typing. It is presently mainly suitable for a limited number of amyloid types, particularly AA since most commercially available antibodies are not reliable. In-house antibodies are often used with better results in laboratories specialized in amyloid diagnostics.
•Western blot analysis. This method can be used on biopsies containing sufficient amount of amyloid. This method is also limited by the availability of suitable antibodies. An advantage is that protein variants can be studied. Protein bands from the SDS-PAGE gel can be cut out and studied by other methods such as mass spectrometry.
•Mass spectrometry. This method is used by a yet small number of specialized laboratories, sometimes after taken out a small amyloid sample with the aid of a laser dissection microscope. So used it offers the possibility of a very precise biochemical diagnosis. The number of laboratories that can use this method is low in all parts of the world and will probably remain so for a fairly long time.
Treatment depends on the biochemical type of systemic amyloidosis.