Proximal renal tubular function in myelomatosis: observations in the fourth Medical Research Council trial

Multiple Facets of Multiple Myeloma in Kidney Biopsy: A Multicenter Retrospective Study

Introduction

Multiple myeloma is a type of plasma cell dyscrasia, which causes clonal proliferation of plasma cells and deposition in various organ systems. At presentation, 50% of patients with multiple myeloma have kidney dysfunction, which is considered a poor prognostic indicator. Data on the histopathological manifestations of multiple myeloma are sparse.

Objective

To look at the kidney histopathological lesions in patients with the clinical diagnosis of multiple myeloma.

Materials and Methods

A retrospective analysis of all kidney biopsies in patients with the clinical diagnosis of multiple myeloma was performed from June 1, 2020 to May 30, 2022, from three tertiary care nephrology referral centers.

Results

A total of 61 patients with multiple myeloma and biopsy-proven kidney involvement were included in the study. The mean age at presentation was 55.39 ± 11.91 years, with male predominance (male to female ratio -1.6:1). The most common lesion on kidney biopsy was myeloma cast nephropathy (72.1%), followed by light chain deposition disease (21.3%) and AL amyloidosis (18%). About 26% of patients had dual lesions on kidney biopsy, 3% had three types of lesions on kidney biopsy In 48% of patients, the diagnosis of multiple myeloma was made only after the kidney biopsy.

Conclusion

Patients with multiple myeloma and kidney involvement should be biopsied as the type of histopathological lesion influences the treatment options and prognosis.

International Myeloma Working Group Recommendations for the Diagnosis and Management of Myeloma-Related Renal Impairment

Purpose

The aim of the International Myeloma Working Group was to develop practical recommendations for the diagnosis and management of multiple myeloma–related renal impairment (RI).

Methods

Recommendations were based on published data through December 2015, and were developed using the system developed by the Grading of Recommendation, Assessment, Development, and Evaluation Working Group.

Recommendations

All patients with myeloma at diagnosis and at disease assessment should have serum creatinine, estimated glomerular filtration rate, and electrolytes measurements as well as free light chain, if available, and urine electrophoresis of a sample from a 24-hour urine collection (grade A). The Chronic Kidney Disease Epidemiology Collaboration, preferably, or the Modification of Diet in Renal Disease formula should be used for the evaluation of estimated glomerular filtration rate in patients with stabilized serum creatinine (grade A). International Myeloma Working Group criteria for renal reversibility should be used (grade B). For the management of RI in patients with multiple myeloma, high fluid intake is indicated along with antimyeloma therapy (grade B). The use of high-cutoff hemodialysis membranes in combination with antimyeloma therapy can be considered (grade B). Bortezomib-based regimens remain the cornerstone of the management of myeloma-related RI (grade A). High-dose dexamethasone should be administered at least for the first month of therapy (grade B). Thalidomide is effective in patients with myeloma with RI, and no dose modifications are needed (grade B). Lenalidomide is effective and safe, mainly in patients with mild to moderate RI (grade B); for patients with severe RI or on dialysis, lenalidomide should be given with close monitoring for hematologic toxicity (grade B) with dose reduction as needed. High-dose therapy with autologous stem cell transplantation (with melphalan 100 mg/m2 to 140 mg/m2) is feasible in patients with RI (grade C). Carfilzomib can be safely administered to patients with creatinine clearance > 15 mL/min, whereas ixazomib in combination with lenalidomide and dexamethasone can be safely administered to patients with creatinine clearance > 30 mL/min (grade A).

Renal failure in myelomatosis

Renal failure is a common presenting feature in myelomatosis. This review offers a practical means for classifying renal failure in this disease. Three groups are identified: (1) those patients whose renal failure improves or is stable when they are maintained on a high fluid intake; (2) the minority of patients whose renal failure progresses despite high fluid intake; and (3) those patients who are fluid-intolerant due to oliguric renal failure or congestive cardiac failure. The difference between groups 1 and 2 is not simply due to differences in response to chemotherapy, for many group-1 patients achieve improvement in renal function without or before loss of light chain proteinuria. It is concluded that all patients with myelomatosis with excess monoclonal free light chain proteinuria are at risk from developing renal failure of the type associated with group 1. The chances of them doing so are diminished if they maintain a high fluid intake. Group 2 encompasses a range of conditions not all of which are clearly defined. There is generally a poor correlation between the physical characteristics of light chains and the presence of group-2 renal failure.

Serum Free Light Chain Analysis and Urine Immunofixation Electrophoresis in Patients with Multiple Myeloma

PURPOSE

Retrospective studies have shown that immunoassays measuring free light chains (FLC) in serum are useful for diagnosis and monitoring of multiple myeloma. This study prospectively evaluates the use of FLC assays and, for the first time, investigates the relationship between serum FLC concentrations and the presence and detectability of Bence Jones (BJ) proteins in the urine.

PATIENTS AND METHODS

Three hundred seventy-eight paired samples of serum and urine were tested from 82 patients during the course of their disease. The sensitivities of serum FLC analysis and urine immunofixation electrophoresis (IFE) in detecting monoclonal FLC were compared. Serum FLC concentrations required for producing BJ proteins detected by IFE were determined.

RESULTS

Abnormal FLC were present in 54% of serum samples compared with 25% by urine tests. In abnormal serum samples for kappa or lambda, the sensitivity of IFE to detect the respective BJ proteins in urine were 51% and 35% and the median serum FLC concentrations required to produce detectable BJ proteins were 113 and 278 mg/L. Renal excretions of monoclonal FLC increased with serum concentrations, but excretions significantly decreased at high serum concentrations combined with renal dysfunction.

CONCLUSION

Serum FLC assays are significantly more sensitive for detecting monoclonal FLC than urine IFE analysis. They also have the advantage of FLC quantification and are more reliable for monitoring disease course and response to treatment.

Urinary proteins and renal dysfunction in patients with multiple myeloma

Besides bone pain, pathologic fractures, anaemia, and recurrent infectious diseases, renal failure is one of the most serious complications in multiple myeloma patients. Its incidence is generally underestimated because of the low reliability of the parameters routinely used for the evaluation of renal dysfunction. Other laboratory tests in the literature are reported to be more suitable to better define the extension of the renal impairment, namely urinary proteins or creatinine clearance. We here report on the clinical implication of urinary parameters in defining the renal function in myeloma patients.

The implication of compromised renal function at presentation in myeloma: similar outcome in patients who receive high-dose therapy: a single-center study of 251 previously untreated patients

The purpose of the study was to determine the role of sequential therapy (ST) in new patients with myeloma presenting with renal dysfunction (RD): serum creatinine >140 micromol/L (1.6 mg/dL). Between April 1985 and June 1998, 251 patients, 59 (23%) with RD were entered into a ST program comprised of infusional chemotherapy (IC) with VAMP/C-VAMP (vincristine, doxorubicin, and methylprednisolone with/without cyclophosphamide) followed by autologous transplantation and interferon maintenance. The median overall survival (OS) of 251 patients from the start of IC was 4.2 yr with the RD group faring significantly poorer (median 2.5 yr) than those with no renal dysfunction (NRD; median 4.6 yr; p = 0.0025). Mortality during the first 100 d of IC was significantly higher in patients with RD (11/59; p = 0.01) compared to patients with NRD. In patients consolidated with high-dose therapy, the OS and event-free survival (EFS) were not significantly different between the two groups. Cox analysis of the variables at presentation failed to show RD as a factor influencing outcome, but it showed that patients with beta-2-microglobulin (beta2M) > or = 3.7 (p < 0.0001), age > or = 52.5 yr (p = 0.002), performance status (PS) > or = 2 (p = 0.005) and patients with light-chain myeloma (p = 0.03) had a significantly shorter OS, beta2M > or = 3.7, PS > or = 2, and light-chain myeloma were predictive of shorter EFS. The study shows that with modern intensive schedules of treatment, renal disease at presentation in isolation does not compromise outcome.

MRC trial of alpha2b-interferon maintenance therapy in first plateau phase of multiple myeloma. MRC Working Party on Leukaemia in Adults

Plateau phase has been achieved in 64% of all newly diagnosed patients with multiple myeloma treated with the ABCM (adriamycin, BiCNU, cyclophosphamide and melphalan) regimen in the Medical Research Council (MRC) trials; this stable clinical stage of the disease is associated with no more than minimal symptoms. Several studies have found that alpha-interferon (alpha-IFN) maintenance therapy increases the duration of plateau phase, but it is less clear if this translates into prolonged survival. We report the effect of alpha-IFN on the duration of plateau phase and overall survival in a trial with 284 patients who were randomized to receive alpha2b-IFN (Intron-A) or no maintenance therapy during first plateau phase. The minimum follow-up after randomization was 21 months. There was no significant difference in the overall survival between the two treatment groups (X2=0.32, P=0.57). There was a trend towards longer relapse-free survival in the patients allocated alpha-IFN, but this trend to longer plateau phase was not statistically significant (X2 = 1.62, P = 0.2). Disease progression at relapse on alpha-IFN appears to be more severe with greater elevations from plateau levels of serum paraprotein (P = 0.06) and beta2-microglobulin (P= 0.03) levels. Physicians tended to start chemotherapy sooner after diagnosis of relapse when patients had received alpha-IFN (P = 0.16). Although, in common with most other studies, there is a trend for patients treated with alpha-IFN to have a longer plateau phase, this is counteracted by morbidity attributable to the treatment and a somewhat shortened survival post relapse. Meta-analysis of interferon trials is required to assess whether the minor trend for longer survival in patients maintained on alpha-IFN found in some studies is significant and, if so, the extent of this advantage.

The role of proteinuria in the progression of chronic renal failure

The cause of the relentless progression of chronic renal failure of diverse origins remains unknown and is likely to be multifactorial. Numerous studies have now demonstrated a correlation between the degree of proteinuria and the rate progression of renal failure, which has led to the hypothesis that proteinuria may be an independent mediator of progression rather than simply being a marker of glomerular dysfunction. This article reviews the evidence underlying this hypothesis and the mechanisms by which particular proteins may cause renal pathology. The abnormal filtration of proteins across the glomerular basement membrane will bring them into contact with the mesangium and with the tubular cells. There is evidence to support a role of lipoproteins on mesangial cell function, which ultimately could contribute to glomerular sclerosis. The proximal tubular cells reabsorb proteins from the tubular fluid, which leaves them particularly vulnerable to any adverse effects proteins may have. It has been postulated that the sheer amount of protein to be metabolized by these cells may overwhelm the lysosomes and result in leakage of cytotoxic enzymes into the cells. In addition, the increased metabolism of proteins may result in production of ammonia, which can mediate inflammation through activation of complement. Specific proteins that have been shown to be cytotoxic are transferrin/iron, low-density lipoprotein, and complement components, all of which appear in the urine in proteinuric states. Other specific proteins have been shown to stimulate production of cytokines, chemoattractants, and matrix proteins by tubular cells and thus may stimulate interstitial inflammation and scarring. The mechanisms by which the presence of proteins in the tubular fluid alters tubular cell biology is yet to be determined.

Renal function in newly diagnosed multiple myeloma--a demographic study of 1353 patients. The Nordic Myeloma Study Group

This study describes the occurrence of renal failure among 1353 newly diagnosed cases of multiple myeloma. Renal function was evaluated by serum creatinine concentration in 1353 cases, 31% of whom had renal failure at the time of diagnosis. In 1206 cases an estimation of creatinine clearance was made. When renal failure was defined by using creatinine clearance estimation, 49% had renal failure at the time of diagnosis. Renal failure was present in 24% of patients with an M component of IgG-, 31% of IgA- and 100% of IgD-type. 52% of patients with light chain disease had renal failure. The frequency of renal failure was similar in lambda- and kappa-light chain disease. Patients with a high excretion of Bence Jones protein in the urine (> 10 g/24 h) had renal failure significantly more often than patients with lower excretion. Renal failure was related to advanced disease; 41% of patients with stage III (Durie-Salmon) disease had renal failure. Renal failure was found in 45% of patients with hypercalcaemia. When estimated creatinine clearance was used as a predictor of renal function, the same trends were found as mentioned above. In addition, the proportion of patients with renal failure was found to increase with advancing age.

Multiple myeloma

Multiple myeloma occurs in over 2000 new patients in England and Wales each year. It presents most frequently as bone pain and patients tend to become dehydrated and may develop renal failure. No available treatment is curative, but about two thirds of patients achieve a stable response with low dose combination chemotherapy. Combination chemotherapy including doxorubicin and carmustine with the alkylating agents cyclophosphamide and melphalan achieve a higher stable response rate than conventional treatment with melphalan and prednisone without additional haematological toxicity. These responses are associated with loss of bone pain and patients remain symptom free for months without further treatment. Relapse occurs on average in a little under two years and, though second responses are frequently obtained, the disease eventually becomes refractory. This paper looks at who should be treated and the benefits that may be expected from the treatments available.

Monoclonal proteins and renal disease

Renal insufficiency, which is present initially in almost half of patients with multiple myeloma, usually results from myeloma kidney or hypercalcemia. Neither the class of light chain nor the isoelectric point plays an important role in kidney failure. Acute renal failure must be treated with appropriate fluids and with electrolytes and hemodialysis if necessary. Plasma exchange may be helpful, but has not been proven as such. The presence of a nephrotic syndrome and a monoclonal kappa or lambda light chain in the urine almost always indicates primary amyloidosis (AL) or light-chain deposition disease. Amyloid fibrils must be distinguished from the fibrils of immunotactoid glomerulopathy.

Differentiation of proteinuria and haematuria by single protein analysis in urine

Single proteins and tubular enzymes have been proposed as markers to detect and differentiate prerenal, glomerular, tubular, and postrenal forms of proteinuria and haematuria. By quantitation of total protein, albumin, alpha 1-microglobulin, IgG, alpha 2-macroglobulin, and N-acetyl-beta, D-glucosaminidase (beta-NAG) activity it has become possible to clearly separate these forms by analysis of a single sample of second morning urine. When this program was applied to screening of hospital patients, albumin, total protein, and NAG proved to be sufficient to exclude clinically relevant disturbances. alpha 1-Microglobulin was useful to separate primary glomerulopathies from tubulo-interstitial diseases. Glomerular and postrenal haematuria could be clearly separated by their different excretion rates of alpha 2-macroglobulin, when urine albumin concentration exceeds 100 mg/L. The results imply that wider application of these techniques can help to detect renal abnormalities at an earlier stage and differentiate the various forms by less invasive techniques.

Urinary excretion of beta 2-glycoprotein-1 (apolipoprotein H) and other markers of tubular malfunction in "non-tubular" renal disease

AIM

To determine whether urinary beta 2-glycoprotein-1 assays can provide improved discrimination between chronic renal diseases which are primarily of tubular or glomerular origin.

METHODS

Urinary beta 2-glycoprotein-1, retinol-binding protein, alpha 1-microglobulin, beta 2-microglobulin, N-acetyl-beta-D-glucosa-minidase and albumin were measured in 51 patients with primary glomerular disease, 23 with obstructive nephropathy, and 15 with polycystic kidney disease, and expressed per mmol of creatinine. Plasma beta 2-glycoprotein-1 was assayed in 52 patients and plasma creatinine in all 89. The findings were compared between the diagnostic groups and with previously published data relating to primary tubular disorders.

RESULTS

All 31 patients with plasma creatinine greater than 200 mumol/l excreted increased amounts of beta 2-glycoprotein-1, retinol-binding protein, and alpha 1-microglobulin, and 29 had increased N-acetyl-beta-D-glucosaminidase; the quantities were generally similar to those found in comparable patients with primary tubular pathology. Among 58 with plasma creatinine concentrations under 200 mumol/l, increases in beta 2-glycoprotein-1, retinol-binding protein, and alpha 1-microglobulin excretion were less common and much smaller, especially in those with obstructive nephropathy and polycystic disease. The ratios of the excretion of albumin to the other proteins provided the clearest discrimination between the patients with glomerular or tubular malfunction, but an area of overlap was present which embraced those with obstructive nephropathy and polycystic disease.

CONCLUSIONS

Increased excretion of beta 2-glycoprotein-1 due to a raised plasma concentration or diminution of tubular reabsorption, or both, is common in all the forms of renal disease investigated, and both plasma creatinine and urinary albumin must be taken into account when interpreting results. Ratios of urinary albumin: beta 2-glycoprotein-1 greater than 1000 are highly suggestive of primary glomerular disease and those less than 40 of primary tubular disease. Used in this way, beta 2-glycoprotein-1 assays provide superior discrimination between glomerular and tubular malfunction when compared with retinol binding protein but the best discrimination is provided by albumin: alpha 1-microglobulin ratios.

Nephrotoxic potential of Bence Jones proteins

BACKGROUND

The renal manifestations of diseases associated with the production of monoclonal light chains--myeloma (cast) nephropathy, light-chain deposition disease, and amyloidosis AL--result from the deposition of certain Bence Jones proteins as tubular casts, basement-membrane precipitates, or fibrils, respectively. For unknown reasons, the severity of the renal manifestations of these diseases varies greatly from patient to patient. We employed an experimental in vivo model to determine the pathologic importance of various Bence Jones proteins.

METHODS

Mice were injected intraperitoneally with 300 mg of Bence Jones protein from 40 patients with multiple myeloma or amyloidosis AL and killed 48 hours later. The mouse kidneys were examined by light and electron microscopy, and light-chain deposits were identified immunohistochemically with highly specific antihuman light-chain antiserum.

RESULTS

Of the 40 different human Bence Jones proteins studied, 26 were deposited in the mouse kidneys predominantly as tubular casts, basement-membrane precipitates, or crystals; no light-chain deposits were detected in the kidneys of the mice that received the other 14 Bence Jones proteins. Of the 18 patients for whom renal tissue was available for study, the findings in 14 were comparable to those in the mice. Furthermore, the proteins obtained from 22 of the 27 patients whose serum creatinine concentrations equaled or exceeded 168 mumol per liter (1.9 mg per deciliter) were deposited in the mouse kidneys, whereas protein deposition occurred after the injection of proteins from only 4 of the 13 patients with serum creatinine concentrations below 168 mumol per liter. The repeated injection of Bence Jones proteins from two patients who had amyloidosis AL resulted in deposition of the protein in the mouse kidneys as amyloid.

CONCLUSIONS

Particular Bence Jones proteins are primarily responsible for producing the distinctive types of protein deposition in renal tissue and the clinical manifestations that occur in patients with light-chain-associated diseases. This experimental model has potential value for the identification of nephrotoxic or amyloidogenic light chains.

Assessment of renal function: selected developments

Tests commonly used to assess the glomerular filtration rate (GFR) and to detect renal tubular damage are critically reviewed. Creatinine clearance which is frequently used for assessment of the GFR is prone to several errors. The plasma creatinine can be used to provide a rough guide but for reliable measurement of the GFR, 51Cr-EDTA clearance is recommended. Measurements of the urinary excretion of low molecular weight proteins, enzymes and kidney tissue proteins have been used to detect tubular damage. Of the low molecular weight proteins excreted, beta-2-microglobulin is unstable and measurement of retinol-binding protein or alpha-1-microglobulin is recommended for the detection of chronic renal tubular malfunction. Of the many enzymes that have been studied, urinary N-acetyl-beta-D-glucosaminidase or alanine aminopeptidase are recommended as being the most useful for the early detection of acute renal tubular damage. Among renal tissue proteins that have been measured in urine adenosine-deaminase-binding protein, a tubular brush border antigen appears to have considerable potential for providing early warning of renal allograft rejection.

Renal impairment in myeloma: negative association with isoelectric point of excreted Bence-Jones protein

The isoelectric point (pI) of the major form of Bence-Jones protein excreted by 62 patients with myeloma and six with macroglobulinaemia was measured by combining isoelectric focusing with immunoblotting techniques. The distribution of the pI values for both kappa and lambda type proteins was bimodal, most falling in the ranges 5.0-6.0 and 7.0-7.5. Plasma creatinine and creatinine clearance and the urine excretion of alpha-1-microglobulin and beta-2-microglobulin were measured in 24 of the patients. These patients, who were free of additional factors known to have an association with the development of renal impairment, were followed up for a mean period of 16 months (range three to 28 months). It was found that renal impairment was not related to the pI of the Bence-Jones protein excreted.

Urinary protein analysis

The differentiation and analysis of urinary proteins has substantially contributed to our knowledge of physiological and pathophysiological processes during glomerular filtration and tubular catabolism of plasma constituents. By use of high-resolution biochemical separation techniques, several urinary polypeptides could be identified as plasma proteins, tissue antigens, tubular enzymes and protein breakdown products. With regard to clinical application, the separation results of conventional gel chromatography and agarose electrophoresis were surpassed by fast protein liquid chromatography and polyacrylamide electrophoresis in one- and two-dimensional systems. In contrast to early one-dimensional polyacrylamide gel electrophoresis (PAGE) methods using homogeneous gels on a macro scale, modern gradient slab gels achieve better resolution over the entire relative molecular mass range of urinary proteins. For clinical demands, the use of micro-scale gradient gels, either laboratory-made or pre-cast, together with an improved Coomassie Brillant Blue staining, offers several advantages, including rapidity, sensitivity and economy. Isoelectric focusing and two-dimensional PAGE, combined with sensitive silver staining and immunoblotting methods, have proved to be valuable tools for the identification and characterization of urinary proteins in defined renal and extra-renal diseases. The quantitative determination of urinary indicator proteins such as albumin and alpha 1- and beta 2-microglobulin can be regarded as a reasonable complement to the pattern diagnosis, especially in the long-term course of renal diseases.

Selective induction of light chain synthesis in cultures of blood lymphocytes from patients with IgG myelomatosis

In the present study evidence is provided that neoplastic B cells from the blood from four of 24 patients with myelomatosis were activated selectively with polyclonal B cell mitogens. In three of these patients the activated cells produced light chains without heavy chains; of these, two patients had IgGK paraproteins and one had free lambda light chain disease. The ratio of kappa-expressing to lambda-expressing B cells in the initial blood B cell preparations was within the range for healthy controls for all four patients where neoplastic B cells were selectively activated. It is concluded that in some patients with myelomatosis the neoplastic clone is a mosaic of: (1) cells capable of synthesizing both light and heavy chains with (2) cells producing light chains only.

Plasma cell dyscrasias: current status

This is a review of the current status of the monoclonal gammopathies (plasma cell dyscrasias). We begin with the recognition of a monoclonal protein in serum and urine. We briefly discuss the differential diagnosis of the monoclonal gammopathies. Clinical and laboratory findings as well as the management of multiple myeloma are addressed. Future approaches for the treatment of myeloma are provided. The variant forms of multiple myeloma, including smoldering myeloma, plasma cell leukemia, nonsecretory myeloma, IgD myeloma, osteosclerotic myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma, are briefly reviewed. Diagnosis and treatment of Waldenström's macroglobulinemia are presented. The recognition and differential diagnosis of the heavy-chain diseases (gamma, alpha, and mu) are included. Monoclonal gammopathy of undetermined significance ("benign" monoclonal gammopathy) is presented in detail. Amyloidosis is not included in this review.

Immunoglobulin light-chain immunoblots of urine proteins from patients with tubular and Bence-Jones proteinuria

Immunoglobulin excretion by patients with monoclonal gammopathies and tubular proteinuria has been analysed by agarose gel isoelectricfocussing of untreated urine and immunoblotting. About three-quarters of the Bence-Jones proteins detected occurred as multiple bands on isoelectricfocussing; in about half of these cases the multiple forms were due to polymerisation or fragmentation of the light chains. In specimens with tubular proteinuria, a characteristic light chain pattern of three broad bands covering the pI ranges 7.1-7.3, 7.8-8.0 and 8.3-8.5 was found. This pattern also occurred in 53% of specimens with Bence-Jones proteinuria and was identical to that found in concentrated normal urine. Intact monoclonal immunoglobulin usually appeared as three or more evenly spaced bands of similar intensity whereas polyclonal intact immunoglobulins produced diffuse staining from pI 5.0-8.5. A scheme for the qualitative analysis of urinary immunoglobulin excretion using this technique has been developed.

Monoclonal gammopathy and multiple myeloma in the elderly

The term 'benign monoclonal gammopathy' indicates the presence of a monoclonal protein in persons without evidence of multiple myeloma, macroglobulinaemia, amyloidosis, lymphoproliferative disease, or other related disorders. The term 'monoclonal gammopathy of undetermined significance' (MGUS) is preferable because it is not known at diagnosis whether an M-protein will remain stable and benign or develop into symptomatic multiple myeloma or related disorders. Immunoelectrophoresis and immunofixation of the serum and urine are necessary to determine the presence and type of M-protein. At the Mayo Clinic, follow-up data have been gathered for more than 13 years on 241 patients with an initial benign monoclonal gammopathy. Nineteen per cent of these patients developed multiple myeloma, macroglobulinaemia, amyloidosis, or related diseases during the follow-up period. There is no reliable technique for differentiating a patient with a benign monoclonal gammopathy from one who will subsequently develop a serious disease. It is necessary to follow these patients indefinitely. Important in the complete understanding of the elderly patient with monoclonal gammopathy are the following: clinical manifestations, laboratory findings, and differential diagnosis of multiple myeloma; the course and prognosis and the induction therapy and treatment of multiple myeloma; newer therapeutic approaches; and the management of complications such as hypercalcaemia, hyperuricaemia, renal failure, bacterial infections, skeletal disease, and neurological problems.

Analysis of serum and urinary retinol binding protein in hepato-renal syndrome

Retinol binding protein (RBP) was analyzed in the sera and urines of 5 patients with hepato-renal syndrome (HRS), 4 with acute tubular necrosis (ATN), 20 liver cirrhosis patients with normal kidney function (NKF), 14 chronic renal failure (CRF) patients, and 19 healthy adults. All renal failure patients had high mean urine RBP (URBP): HRS, 8 mg/L; ATN, 11 mg/L; CRF, 8 mg/L respectively; p less than 0.001 vs the rest. Those with ATN and CRF had high mean serum RPB (SRBP): 146 and 149 mg/L, respectively, p less than 0.001 compared to the other groups. In HRS, in spite of renal failure, SRBP was very low (mean = 12 mg/L). The cirrhotics with NKF averaged less than 50% of the SRBP values of the healthy controls (16 vs 41 mg/L RBP, p less than 0.001); their RBP excretion was normal (mean URBP of 0.1 vs 0.06 mg/L in the control group). RBP analyses before and during HRS in two patients showed a marked increase in urine RBP during HRS (35- and 600-fold respectively) with practically unchanged serum levels. Impaired hepatic production and/or release is proposed to explain the low serum RBP in HRS, and a renal tubular injury or dysfunction to account for its high excretion. The RBP urinary loss could further compromise an already abnormal RBP metabolism and its serum levels. This combination (of low serum and high urine RBP), in the context of renal failure occurring in alcoholic liver cirrhosis, could help in the recognition of HRS.

N-acetyl-beta-D-glucosaminidase enzymuria in leukaemia and myelomatosis: effect of treatment in acute myeloblastic leukaemia and myelomatosis in adults

The activity of the lysosomal hydrolase N-acetyl-beta-D-glucosaminidase (NAG) was measured in the urine of patients with leukaemia or myeloma. Elevated pre-treatment enzymuria was noted in all patient groups with acute myeloblastic leukaemias (AML) FAB type M4 or 5 displaying higher activities than AML patients FAB types M1-3, which in turn were higher than those found in patients with myelomatosis and chronic lymphocytic leukaemia. The ratio of the major isoenzymes of NAG, A/B was reduced significantly only in patients with AML. Following treatment, AML patients who entered remission demonstrated NAG levels which approached normal values. In those AML patients who were either in relapse, in the terminal phase of their illness or treated with aminoglycoside antibiotics, NAG enzymuria was similar to pre-treatment values. A reduction in urinary NAG levels and both serum and urine beta 2 microglobulin concentrations was also observed following treatment in myeloma patients. The use of enzymuria both as a guide to progress towards remission in AML patients and for assessing prognosis and progress in myeloma patients is discussed.

Isoelectric points of urinary light chains in myelomatosis: analysis in relation to nephrotoxicity

Measurements of the isoelectric point (pI), sialic acid content, and polymerisation were made of 43 light chains isolated from the urine of patients with myelomatosis excreting large amounts of light chains. The pIs ranged from 3.5-9.5, and 23 were greater than 7.0. Sialylation was detected in 62% of light chains, and 69% showed microheterogeneity of charge. There was no clear association between the pI, sialylation, or polymerisation and the presence of renal failure, as assessed by serum creatinine concentrations. Light chains with pI spectrotype in the basic range, however, were found to produce more proximal tubular dysfunction than acidic light chains.

Detection of Bence-Jones protein by isoelectric focussing of unconcentrated urine followed by nitrocellulose blotting and immunoperoxidase staining

Urine specimens from 164 patients sent to the laboratory for testing for Bence-Jones proteinuria were investigated using a new procedure. The protein in the untreated urine was subjected to isoelectric focussing in an agarose gel, transferred to a nitrocellulose membrane by blotting, and then stained by an immunoperoxidase technique for either immunoglobulin kappa or lambda chains. This technique was compared with a routine procedure for the detection of immunoglobulin light chains involving concentration by ultrafiltration, electrophoresis and then immunofixation. The new technique achieved a much increased rate of detection of Bence-Jones proteinuria. Among 51 patients known to have myeloma or macroglobulinaemia, Bence-Jones proteinuria was detected in 35 cases with the new procedure and in only 27 by the conventional method. In 28 patients with paraproteinaemia without other evidence of myeloma, macroglobulinaemia, leukaemia or lymphoma, 12 instances of Bence-Jones proteinuria were discovered with the new procedure, 10 of which were missed by the conventional method. The improved efficiency of detection is attributed to the high resolution of isoelectric focussing and the avoidance of protein loss from adsorption on to ultrafiltration membranes.

Objective evaluation of the role of vincristine in induction and maintenance therapy for myelomatosis. Medical Research Council Working Party on Leukaemia in Adults

In the Medical Research Council's IVth trial in Myelomatosis the possible benefit of adding vincristine to first line treatment with intermittent melphalan and prednisone has been assessed. This was analysed in 530 patients who were randomly allocated to receive vincristine or not. Survival was not improved by the addition of vincristine. A total of 268 patients reached plateau phase on first line therapy. Of these 226 patients were rerandomised either to continue receiving first line therapy for a further year or to cease therapy. At the present time there is a slight but not significant survival advantage in the group which received no further treatment on reaching plateau.

Fast protein liquid chromatography scale-up procedures for the preparation of low-molecular-weight proteins from urine

A system for the rapid isolation of low molecular weight proteins from urine has been devised, and illustrated by alpha 1-microglobulin, beta 2-microglobulin, retinol binding protein, lysozyme and monoclonal light chains. Urine proteins from patients with tubular dysfunction were concentrated, either by ultrafiltration or ammonium sulphate precipitation. This was followed by gel chromatography on Sephadex G-50. The appropriate fractions were then separated by chromatography on Pharmacia monobead columns. A Mono Q strong anion exchanger was used for beta 2-microglobulin, retinol binding protein, alpha 1-microglobulin and free monoclonal light chains. Lysozyme was separated on a Mono S cation exchanger. The chromatography was first optimized on HR 5/5 columns and then scaled up to HR 16/10 columns.