Aim: To study the pathomorphology of kidneys in patients with multiple myeloma (MM) and severe renal failure (RF) and to compare the results of morphological, immunohistochemical, and electron microscopic examinations of nephrobiopsy specimens with the pattern of monoclonal secretion and the type of proteinuria and paraproteinuria.
Subjects and methods: A study group comprised 25 patients with MM and severe RF; 22 of them underwent programmed hemodialysis. Immunochemical study of serum and urine proteins, renal puncture biopsy with light, immunofluorescence and electron microscopy examination of its specimens were performed in all the patients.
Results: Cast nephropathy (CN) is the most common type of renal impairment in patients with MM and severe RF. CN concurrent with monoclonal immunoglobulin deposition disease was identified in 32% of cases. In the mixed lesion, it is CN that is a determinant in the development of acute and chronic RF. Rare variants of nephropathies as fibrillary glomerulonephritis, immunotactoid nephropathy, and crystalline histiocytosis were found in 16% of cases. In most cases, severe RF in MM develops in case of low monoclonal secretion. However, there are a larger number of secreted and excreted monoclonal light chains in CN than in other variants of kidney lesion. Urinary paraprotein G excretion suggests that the glomerular filter is damaged. Degenerative changes in the podocytes and a reduction in their small processes were detected in the majority of cases. In glomerular or mixed proteinuria, there were also unorganized and organized deposits in the glomerular basement membrane.
Conclusion: The pattern of nephropathy does not determine a renal response after chemotherapy. The reversibility of CN in MM depends on the magnitude of interstitial fibrosis and podocyte changes. The pronounced changes in the podocytes as a reduction in their small processes serves as a poor sign in achieving renal responses following chemotherapy.