Fibrillary glomerulonephritis associated with monoclonal gammopathy of undetermined significance showing lambda-type Bence Jones protein

Fibrillary Glomerulonephritis and Monoclonal Gammopathy: Potential Diagnostic Challenges

Fibrillary glomerulonephritis (FGN) is a rare glomerular disease featured by the randomly arranged 12- to 24-nm fibrils under electron microscopy (EM). Up to 10% of FGN patients have monoclonal gammopathy. However, distinguishing between FGN as monoclonal gammopathy of renal significance (MGRS) and FGN from other causes with incidental monoclonal gammopathy of undetermined significance (MGUS) can be challenging, as the current way of demonstrating monoclonality is flawed due to (1) the suboptimal sensitivity of kappa staining by immunofluorescence in frozen tissue (IF-F) as compared to pronase-digested paraffin sections (IF-P), causing incorrect labeling of light chain restriction; (2) the unavailability of immunoglobulin G (IgG) subtyping in some centers; and (3) the unavailability of tests demonstrating the monoclonality of highly variable VH or VL domains in immunoglobulin structures in clinical use. The discovery of DnaJ homolog subfamily B member 9 (DNAJB9) allows diagnosis for FGN with less reliance on EM, and the summary of recent studies revealed that genuine MGRS is extremely rare among FGN. Further research integrating IF-P, IgG subtyping, VH or VL domain monoclonality confirmation, and DNAJB9 as diagnostic modalities, with corresponding clinical data including treatment response and prognosis, is required for a better understanding of this subject.

New aspects on the pathogenesis of renal disorders related to monoclonal gammopathies

BACKGROUND

Multiple myeloma and other related monoclonal gammopathies are frequently encountered conditions associated with renal damage, especially in elderly population. They are arising from clonal proliferation of plasma cells in bone marrow producing various quantities of abnormal monoclonal immunoglobulins, or their components/fragments.

SUMMARY

These abnormal proteins differ from normal immunoglobulins in the amino acid sequence and in the three-dimensional structure of the molecule, which may determine their toxicity. Kidney seems to be a target organ as a major catabolic site. The pathology of renal disease is highly heterogeneous involving a variety of different mechanisms, which are divided into immunoglobulin dependent and immunoglobulin independent mechanisms. The Ig-dependent mechanisms may involve the four components of the kidney parenchyma, and the primary structure of these proteins determine the pattern of renal disease.

KEY MESSAGE

This review summarizes the existing literature in the pathobiology of multiple myeloma, and the pathological properties of the M-proteins, focusing on the mechanisms of the renal manifestations related to these abnormal proteins, especially glomerular injury. Also it supports the opinion that monoclonal gammopathy of undetermined significance (MGUS) should not be used in cases where there is proven renal impairment due to these proteins, even if it is mild and does not meet the current criteria.

Acute kidney injury in a patient with polyarteritis nodosa and multiple myeloma

We herein report the case of a Japanese man with polyarteritis nodosa (PAN) accompanied by multiple myeloma (MM). The patient was diagnosed with PAN. Concurrently, IgG kappa paraprotein was detected, and bone marrow changes indicative of MM were observed. Prednisolone (PSL) administered at a dose of 30 mg/day was initiated; however, the serum creatinine level increased. In spite of increasing the dose of PSL to 45 mg/day and initiating treatment with double filtration plasmapheresis, the patient's renal dysfunction continued to progress and haemodialysis was introduced. He died from pneumonia 12 months after admission. We conclude that renal failure is an important risk factor in the prognosis of PAN accompanied by MM.

Monoclonal gammopathy of renal significance: when MGUS is no longer undetermined or insignificant

Multiple myeloma is the most frequent monoclonal gammopathy to involve the kidney; however, a growing number of kidney diseases associated with other monoclonal gammopathies are being recognized. Although many histopathologic patterns exist, they are all distinguished by the monoclonal immunoglobulin (or component) deposits. The hematologic disorder in these patients is more consistent with monoclonal gammopathy of undetermined significance (MGUS) than with multiple myeloma. Unfortunately, due to the limitations of the current diagnostic schema, they are frequently diagnosed as MGUS. Because treatment is not recommended for MGUS, appropriate therapy is commonly withheld. In addition to end-stage renal disease, the persistence of the monoclonal gammopathy is associated with high rates of recurrence after kidney transplantation. Preservation and restoration of kidney function are possible with successful treatment targeting the responsible clone. Achievement of hematologic complete response has been shown to prevent recurrence after kidney transplantation. There is a need for a term that properly conveys the pathologic nature of these diseases. We think the term monoclonal gammopathy of renal significance is most helpful to indicate a causal relationship between the monoclonal gammopathy and the renal damage and because the significance of the monoclonal gammopathy is no longer undetermined.

Coexistence of fibrillary glomerulonephritis in a patient with multiple myeloma

A 71-year-old man was admitted to our hospital for two weeks due to edema in both legs. A bone marrow aspiration test confirmed a diagnosis of multiple myeloma. The result of the patient's renal biopsy showed fibrillary glomerulonephritis (FGN). FGN is a rare form of glomerulopathy that is diagnosed using electron microscopy when deposits of amyloid-like fibrils are observed on the mesangium and microvascular wall. These fibrils do not respond to Congo red staining and are generally 12-30 nm in diameter. This is a report of an unusual case of fibrillary glomerulonephritis in a patient with multiple myeloma.

Development of Renal Failure without Proteinuria in a Patient with Monoclonal Gammopathy of Undetermined Significance: An Unusual Presentation of AL Kappa Amyloidosis

AL amyloidosis complicating monoclonal gammopathy of undetermined significance (MGUS) has usually a predominant glomerular deposition of lambda light chain. Heavy proteinuria is one of its cardinal manifestations. A 78-year-old man with a 9-year history of IgG kappa light-chain-MGUS and normal urine protein excretion developed severe renal failure. Serum levels of kappa light chain and serum IgG had been stable while proteinuria was absent throughout the nine-year period. For the first eight years, he had stable stage III chronic kidney disease attributed to bladder outlet obstruction secondary to prostatic malignancy. In the last year, he developed progressive serum creatinine elevation, without any increase in the serum or urine levels of paraproteins or any sign of malignancy. Renal ultrasound and furosemide renogram showed no evidence of urinary obstruction. Renal biopsy revealed AL amyloidosis, with reactivity exclusive for kappa light chains, affecting predominantly the vessels and the interstitium. Glomerular involvement was minimal. Melphalan and prednisone were initiated. However, renal function continues deteriorating. Deposition of AL kappa amyloidosis developing during the course of MGUS predominantly in the wall of the renal vessels and the renal interstitium, while the involvement of the glomeruli is minimal, leads to progressive renal failure and absence of proteinuria. Renal biopsy is required to detect both the presence and the sites of deposition of renal AL kappa light chain amyloidosis.