Correlations between the morphological and clinical findings in a patient recovering from secondary generalised amyloidosis with renal involvement. Light- and electron microscopic investigations on serial biopsies.

We report light- and electron microscopic findings in glomerular amyloidosis (secondary amyloidosis), which occurred after recurrent empyema of the pleura. After healing of the empyema, the clinical symptoms disappeared, over a period of eight years. During the acute stage of the disease (grade II-III amyloidosis) when the nephrotic syndrome was present, amyloid deposits were seen in the mesangium and on both sides of the basement membrane of the glomerular capillaries. Furthermore, denuded basement membrane areas showing the passage of amyloid into the urinary space, and invaginations of the podocyte by straightened amyloid fibrils were found. After clinical recovery (except for a trace of proteinuria), the renal amyloidosis had electronmicroscopically transformed from an active into an inactive or resting form, while the amount of amyloid present was almost the same. In the areas of amyloid deposits, reparative changes were observed, espcially in the area of the mesangial cells and of the podocytes. The podocytes were separated from the persisting amyloid deposits by newly formed basement membrane material.