CARDIAC IMMUNOCYTE-DERIVED (AL) AMYLOIDOSIS - AN ENDOMYOCARDIAL BIOPSY STUDY IN 11 PATIENTS

The objective of this study was to investigate the spectrum of morphol ogic features in myocardial biopsy specimens from patients with cardia c immunocyte-derived (AL) amyloidosis. Cardiac involvement is the most important predictor of survival in AL amyloidosis. Myocardial biopsy remains the method of choice for diagnosing cardiac amyloidosis when n oninvasive studies give equivocal results. Histologic, immunohistochem ical, ultrastructural, and morphometric studies were made on myocardia l biopsy specimens from 11 patients in whom the diagnosis of AL amyloi dosis was based on the demonstration of a monoclonal immunoglobulinopa thy and of amyloid deposits in tissues. Histopathologic study showed a myloid in 10 of the 11 biopsies. In one biopsy (Congo red negative), t he diagnosis was made by ultrastructural identification of amyloid fib rils. In ail patients, the deposits formed perimyocytic layers that me asured up to 18 mu m in thickness. These layers formed along the basem ent membranes, which were partially preserved in 5 patients and unreco gnizable in 6. Interstitial nodular deposits were also present in 5 pa tients. Immunohistochemical studies for the characterization of the pr oteins in the amyloid deposits were diagnostic in 1 patient and confir matory in 10. Nodular deposits, thick perimyocytic layers of amyloid a nd small myocyte diameters were associated with shorter survival of th e patients. Small-vessel involvement and myofilament loss occurred in all patients. In conclusion, myocardial biopsy serves to (1) establish the diagnosis of cardiac amyloidosis; (2) characterize immunohistoche mically the proteins in the amyloid fibrils and (3) assess the degree of myocyte damage and atrophy.