Acute kidney injury due to tubular intraluminal monoclonal light chain crystals mimicking acute pyelonephritis

Successful renal recovery from multiple myeloma-associated crystalline light chain cast nephropathy and accompanying acute kidney injury with early use of bortezomib-based therapy: a case report and literature review

Crystalline light chain cast nephropathy is a rare distinct morphologic variant of light chain cast nephropathy which is the most common renal lesion associated with multiple myeloma. It is often related to high myeloma tumor burden, severe acute kidney injury, and an unfavorable prognosis. A 79-year-old Japanese man was referred to our medical center with anemia, proteinuria, and acute exacerbation of the serum creatinine accompanying anuria. A renal biopsy showed crystalline cast filling the tubular lumens, injured tubular cells, and inflammatory cells infiltration of interstitium. Serum and urine immunofixation detected a monoclonal protein (IgA-λ and Bence-Jones Protein-λ, respectively), and bone marrow examination observed 64% of plasma cells. IgA-λ type multiple myeloma-associated crystalline light chain cast nephropathy and accompanying acute kidney injury were confirmed. Hydration and emergency hemodialysis were immediately introduced, and the treatment with bortezomib and dexamethasone was initiated. The patient showed successful recovery in renal manifestations. We suggest that early use with bortezomib-based therapy should be considered for patients with acute kidney injury caused by multiple myeloma-associated crystalline light chain cast nephropathy.

Crystalline appearance in light chain cast nephropathy is associated with higher early mortality in patients with newly diagnosed multiple myeloma

BACKGROUND

Light chain cast nephropathy (LCCN) is the most common kidney lesion in multiple myeloma patients. LCCN may exhibit a crystalline appearance. The frequency and clinical significance of crystalline LCCN are not well understood. Here, we report the first retrospective study of crystalline LCCN.

METHODS

Twenty-six patients with LCCN were enrolled. We studied the clinicopathological features and outcomes of LCCN patients and compared ordinary LCCN patients (n = 18) with crystalline LCCN patients (n = 8).

RESULTS

Crystalline LCCN was not rare (8/26, 30.8%) in our study. The median age of LCCN patients was 57.5 (range, 41-75) years. No patients presented with nephrotic syndrome. No significant differences in clinical features were observed between the two groups. All crystalline LCCN patients suffered from advanced multiple myeloma and acute kidney injury. There was a dominance of the λ isotype (7/8, 87.5%) in patients with crystalline LCCN. Patients with ordinary LCCN had significantly higher scores of tubular atrophy and acute tubular injury than those with crystalline LCCN. The crystalline casts of 5 crystalline LCCN patients stained negative with antihuman Tamm-Horsfall glycoprotein. There were no significant differences in the median overall survival between the crystalline LCCN group and the ordinary LCCN group (6.0 months vs. 35.0 months, p = 0.173). However, crystalline LCCN patients had higher early mortality than ordinary LCCN patients (50.0% vs 11.1%, p = 0.03).

CONCLUSION

Crystalline LCCN patients had higher early mortality than ordinary LCCN patients. Thus, for patients with LCCN, crystalline appearance should be screened carefully.

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

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.