Two kinds of rare light chain cast nephropathy caused by multiple myeloma: case reports and literature review

Abstract

Background Light chain cast nephropathy (LCCN) is the most common renal disease caused by multiple myeloma (MM). In addition to ordinary light chain protein casts, there are a few rare casts with unique shapes, including light chain amyloid casts (LCAC) and light chain crystal casts (LCCC). Case presentations Here, we report two patients. Patient 1 is a 72-year-old man who was clinically diagnosed with MM and acute kidney injury (AKI). Pathological examination of a renal biopsy revealed that there were many amyloid casts in the distal tubules that had a lightly-stained central area and a deeply-stained burr-like edge. The marginal zone of the cast was positive for Congo red staining and contained numerous amyloid fibers, as observed by electron microscopy. No systemic amyloidosis was found. The patient received 4 courses of bortezomib-based chemotherapy, and then, his MM achieved partial remission. Patient 2 is a 57-year-old man who was also clinically diagnosed with MM and AKI. Pathological examination of a renal biopsy showed that there were many crystalline casts in the distal tubules that were fully or partially composed of crystals with different shapes, including rhomboid, needle, triangle, rectangle and other geometric shapes. Congo red staining was negative. Crystals were also detected in the urine of this patient. After 9 courses of treatment with a bortezomib-based regimen, his MM obtained complete remission and his renal function returned to normal. Conclusions LCAC and LCCC nephropathy caused by MM are two rare types of LCCN, and both have their own unique morphological manifestations. LCAC nephropathy may not be accompanied by systemic amyloidosis. The diagnosis of these two unique LCCNs must rely on renal biopsy pathology, and the discovery of urine crystals is of great significance for indicating LCCC nephropathy.

Kidney Transplantation and Clinical Outcomes in Patients With Multiple Myeloma: Evidence From the United States Nationwide Inpatient Sample

“…This condition is primarily characterized by the formation of clear cylinders and proximal tubular damage, which are caused by free light chains in the urine [ 20 ]. There are also other subsets of patients with kidney involvement who develop monoclonal immunoglobulin deposition disease [ 21 ].…”

Kidney Biopsy Corner: Amyloidosis

“…This is likely because the majority of the abnormal protein is deposited in tissues. In addition to depositing in the glomeruli, interstitium, and vessels, amyloidogenic cast nephropathy can be seen in rare cases [ 31 ]. Similarly, intratubular cytoplasmic AL amyloidosis is associated with extrarenal amyloidosis [ 32 ].…”