EHA Library - The official digital education library of European Hematology Association (EHA)

Light chain (AL) amyloidosis is a deposition disease with can affect many organs and with a variable but usually bad, prognosis. Therapy requires a quick and correct diagnosis. Accurate identification of amyloid deposition and of the amyloid subtype in tissue biopsies is thus, mandatory. Random biopsies of easily accessible tissues such as subcutaneous fat, gingivae or rectum are usually recommended but sensitivity of this approach is low.

We reviewed all tissue biopsies performed during the study period (2004-2017) in 62 consecutive patients diagnosed of AL amyloidosis at the same center. A bone marrow (BM) biopsy was performed per protocol in all cases. Decisions on biopsies were taken considering organ involvement and accessibility: skin, lymph nodes, lung or tongue biopsies were performed when lesions were seen on clinical or X-ray examinations, cardiac biopsies in the presence of increased NT-proBNP (N-terminal natriuretic peptide) levels and typical echocardiographic findings, kidney biopsies in patients with nephrotic syndromes. Biopsies were stained with Congo Red and read under polarized light with a Texas filter. Subtyping of the amyloid was done using anti-kappa, anti-lambda, anti-TTR and anti-A antisera.

If any biopsy was positive for AL amyloid, no further biopsies were performed unless necessary for therapeutic decisions.

Prognosis in AL amyloidosis is slowly improving with the use of new anti-myeloma drugs and may improve further with new monoclonal antibodies. Therapy requires an early and accurate diagnosis. We do not perform random biopsies of tissues such as fat or gingivae due to low sensitivity. In our hands biopsies of tissues or organs with clinical, analytical or radiological involvement shows higher sensitivity. A bone marrow biopsy is required for diagnosis of the neoplastic disease underlying AL amyloidosis and may show amyloid in up to 50% of the cases. Cardiac biopsy is also highly sensitive and in centers with a high degree of expertise such as ours, has no complications. Our data allow us to recommend a different approach to AL amyloidosis of what is usually published. Biopsies of clinically involved organs yields almost 100% sensitivity. Random biopsies of gingivae, subcutaneous fat or rectum should be discouraged.