Beta-2-microglobulin-derived amyloidosis: onset, distribution and clinical features in 13 hemodialysed patients

Beta2-microglobulin amyloidosis in hemodialysis and peritoneal dialysis patients

Beta(2)-microglobulin (beta(2)-M) amyloidosis is an important cause of morbidity in patients on dialysis. In this cross-sectional study, we evaluated supraspinatus tendon thickness (as a measure of shoulder involvement from beta(2)-M amyloidosis) in patients who are on hemodialysis (HD) compared with those on continuous ambulatory peritoneal dialysis (CAPD). In 27 patients on HD who were treated with high-flux dialyzers, 31 patients on CAPD, and 31 healthy volunteers, we performed bilateral shoulder magnetic resonance imaging and measured the supraspinatus tendon thickness using electronic calipers. There were no statistically significant differences in age or dialysis duration between the HD and CAPD patients. Each patient was asked about the presence or absence of shoulder pain. The supraspinatus tendon thickness in HD patients (mean thickness 6.6 +/- 1.3 mm, range 3.20-8.80 mm, N = 53) and CAPD patients (6.8 +/- 0.9 mm, range 4.9-8.8 mm, N = 61) was not significantly different (P = 0.289); however, the mean thickness in either group was higher than in the healthy controls (5.5 +/- 0.6 mm, range 4.3-6.8 mm, N = 61) (HD patients vs. controls: P = 0.000; CAPD patients vs. controls: P = 0.000). Patients with shoulder pain had higher mean supraspinatus tendon thickness measurements than patients without shoulder pain (P = 0.042). The thickness of supraspinatus tendons is not significantly different between patients on CAPD and HD. An association exists between shoulder pain and mean supraspinatus tendon thickness. This hidden complication of ESRD should be further studied in larger populations of dialysis patients.

Pleural involvement of dialysis-related amyloidosis

Two cases of pleural involvement of dialysis-related amyloidosis (DRA) with pleural effusion are presented. DRA is one of the most important complications in long-term dialysis patients and beta2-microglobulin is the principal protein component of DRA, but pleural deposition of beta2-microglobulin amyloid has not yet been reported. To the best of the authors' knowledge, this is the first case report of pleural involvement of DRA presenting with pleural effusion. This case study suggests that pleural involvement of DRA should be considered when exudative pleural effusion is observed in patients undergoing long-term dialysis.

Studies on unfolded β2-microglobulin at C-terminal in dialysis-related amyloidosis

BACKGROUND

In 1997, Stoppini et al reported that monoclonal antibody specific to the C-terminal 92-99 of beta(2)-microglobulin (beta(2)m) had been capable of inhibiting fibrillogenesis of beta(2)m in vitro. Meanwhile, recent studies have indicated that an acidifying procedure can unfold conformation of the precursor protein, leading to fibril formation of beta(2)m as well as a transthyretin.

METHODS

We thus prepared monoclonal antibody specific to the C-terminal 92-99 (mAb 92-99), and investigated its reactivity in plasma ultrafiltrate and amyloid tissues from 18 hemodialysis patients with dialysis-related amyloidosis (DRA).

RESULTS

beta(2)m extracted from ultrafiltrate showed no reaction for mAb 92-99, whereas acidified beta(2)m from ultrafiltrate showed a reaction for mAb 92-99. Similarly, a homogenate of carpal amyloid tissues showed a strong reaction for mAb 92-99 on immunoblotting. Immunohistochemical study showed also a distinct staining for mAb 92-99 in 7 Congophilic specimens from DRA patients. More interestingly, staining for mAb 92-99 could be found in most, though not all, non-Congophilic tissues.

CONCLUSION

This study demonstrates that the monoclonal antibody specific to the C-terminal 92-99 of beta(2)m can detect the conformational intermediate in amyloidogenesis of beta(2)m ex vivo, and demonstrates that an unfolded beta(2)m at C-terminal could be found not only in Congophilic area but even in non-Congophilic area as well.

Effect of hemodialysis membranes on beta 2-microglobulin amyloidosis

Early after the identification of beta(2)-microglobulin amyloidosis (A beta(2)M) as the cause of carpal tunnel syndrome, it was thought that hemodialysis was a major cause in the development of the disease. It was subsequently shown that hemodialysis was not necessary for the development of dialysis-related amyloidosis; however, it was believed that the different dialysis membranes did modulate the progression of the disease. Current data demonstrate that hemodialysis fails to prevent or reverse the disease, but there is substantial evidence that high-flux, high-efficiency dialyzers slow its progression. Many factors related to hemodialysis have been evaluated in relation to A beta(2)M, including the effect of the bioincompatibility of the membrane, the capacity of the different membranes to remove beta(2)M, and the effect of reuse on beta(2)M levels. Moreover, there have been intensive efforts to evaluate, explore, and improve the different mechanisms in beta(2)M removal, with adsorption as a promising prospect. With the available evidence, it seems that the removal of beta(2)M by the membrane plays the most important role in modulating the disease outcome and rate of progression, although a large, long-term, multicentered and randomized study is still lacking to prove this relationship. However, it is possible that with the continuing advances in optimizing the beta(2)M removal efficiency of the different membranes, the frequency and severity of the disease can be substantially decreased.

Histological prevalence of beta 2-microglobulin amyloidosis in hemodialysis: a prospective post-mortem study

The histological prevalence of beta-2 microglobulin amyloidosis (A beta 2m) was evaluated in a prospective study of joint samples obtained at autopsy in 54 patients on hemodialysis (HD) for 2 to 163 (median 47) months, aged 20 to 80 (median 63) years at HD onset. Carpal tunnel syndrome surgery or radiological signs of A beta 2m were present in 2 and 4% of them, respectively. A control group of 34 patients without end-stage renal disease, autopsied during the same period was used as a reference. The 153 sampled joints (1 to 8, median 2 per patient) were sternoclavicular joints (N = 77), shoulders (N = 35), knees (N = 28), others (N = 13). A beta 2m was diagnosed (positive Congo red with typical birefringence and positive immunostaining of deposits for beta 2m) in 26 of 54 (48%) patients. Prevalence reached respectively 21%, 33%, 50%, 90% and 100% within two years, after 2 to 4 years, 4 to 7 years, 7 to 13 years and more than 13 years HD. The calculated sensitivity of the various joints for A beta 2m detection is significantly higher (P < 0.03) for sternoclavicular joints (97%) and knees (91%) than for shoulders (57%). Multivariate stepwise logistic regression with discriminant analysis identified both HD duration (P = 0.0008) and age at HD onset (P = 0.0093) but not diabetic nephropathy (P = 0.23) or gender (P = 0.25) as independent risk factors for A beta 2m. The probability of joint A beta 2m was quantitated as a function of age and HD duration. In conclusion, A beta 2m may be observed in the large joints early after HD onset. Overall prevalence reaches 48% of the patients on HD for a median of 47 months. It is much higher than that reported on the basis of clinical or radiological evidence. The sternoclavicular and knee joints are more frequently (P < 0.03) involved than the shoulder. The easily accessible sternoclavicular joint therefore appears to be the best site for the early detection of A beta 2m. Both HD duration and age at HD onset, but not diabetic nephropathy, are independent risk factors for A beta 2m.

Spontaneous tendon ruptures in patients on chronic dialysis

Large tendon rupture is a rare catastrophic occurrence in dialysis patients. Pathogenesis of this has been variably thought to be due to malnutrition, insufficient dialysis, amyloidosis, chronic acidosis, or hyperparathyroidism. We investigated contributory causes and timing of this complication in 44 dialysis patients (42 hemodialysis and two peritoneal dialysis patients). Five cases were our own; the other 39 were reported in the literature during the last two decades. Data were compared with a hospital database of 916 patients. The patients who experienced tendon ruptures had been on dialysis longer (mean duration, 7.6 years v 4.0 years; P = 0.001), were younger (mean age, 39.7 years v 48.4 years; P = 0.0001), had much higher parathyroid hormone levels (1,802 pg/mL v 202 pg/mL; P = 0.0001), had a higher phosphate level (6.8 mg/dL v 5.9 mg/dL; P = 0.001), had a slightly higher calcium level (9.2 mg/dL v 8.8 mg/dL; P = 0.038), and had a higher alkaline phosphatase level (649 IU/L v 109 IU/L; P = 0.0001) than control patients. Patients with tendon ruptures had no evidence of malnutrition (albumin 3.7 g/dL v 3.8 g/dL; P = 0.237) and had the same acidosis (bicarbonate 22.2 mEq/L v 22.0 mEq/L; P = 0.180). The time on dialysis to rupture was inversely related to the patient's age (r = 0.47, P = 0.004). Most patients had evidence of years of poorly controlled hyperparathyroidism with high and increasing levels of parathyroid hormone and alkaline phosphatase. Previous steroid use was also much more common in patients with tendon ruptures, as was radiographic evidence of osteitis fibrosa. The disease led to long hospitalization and prolonged morbidity, with mobility limitations in several patients. Spontaneous large tendon rupture in patients is secondary to hyperparathyroidism; is more common in young patients, particularly if exposed to corticosteroids; leads to long-lasting morbidity; and should be preventable by better supervision and treatment of hyperparathyroidism.

Peripheral nerve amyloidosis

Peripheral nerve amyloidosis is the cardinal feature of familial amyloid polyneuropathy (FAP) but can also be seen in primary light chain (AL) amyloidosis and dialysis (beta 2-microglobulin) related amyloidosis. The generalized neuropathy seen in all forms of peripheral nerve amyloidosis is similar, characterized by a severe progressive mixed neuropathy with autonomic dysfunction. Pathologically, amyloid is found in the peripheral nervous system as amorphous, eosinophilic, extracellular deposits. FAP is most commonly associated with variant plasma transthyretin (TTR), although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now at least 36 point mutations in the TTR gene associated with FAP and these continue to be described. Recent studies on the possible role individual point mutations in the TTR gene may play in amyloidosis have helped give us an insight into the mechanisms behind peripheral nerve amyloidosis. This article reviews the clinical and pathological features of the peripheral nerve amyloidosis and discusses theories of amyloidogenesis based on studies of FAP.

Spinal cord compression in renal osteodystrophy

A patient undergoing regular haemodialysis for chronic renal insufficiency developed neck pain followed by progressive spinal cord compression due to subluxation at the level C3-4. Decompression, laminectomy and osteosynthesis led to an almost complete recovery. A review of all the histological specimens suggested that hyperparathyroidism and not amyloidosis caused the vertebral destruction.

Dialysis-associated amyloidosis

Dialysis-related arthropathy represents a major complication of uremic patients treated by hemodialysis or other renal replacement therapies. Nearly 10 years ago, this syndrome was shown to be associated with a new type of amyloid, mainly composed of beta-2 microglobulin (beta 2-M). Retention of the beta 2-M protein due to chronic renal failure, although unquestionably a prerequisite for the occurrence of beta 2-M amyloidosis, appears not to be the unique pathogenetic factor involved in this complication. A role has also been attributed to an enhanced local or systemic generation of inflammatory mediators, an increased production of beta 2-M, and an altered metabolism of the molecule including partial proteolysis and glycation. It is possible that factors related to renal replacement therapy such as dialysis membrane biocompatibility also play a role. However, the clarification of the precise underlying mechanism(s) awaits further study. Because dialysis technology has progressed considerably during the last decade, a significant beta 2-M removal can be achieved at present using high-flux dialyzers. Moreover, a marked reduction in bioincompatibility during the dialysis procedure as manifested by activation of complement and stimulation of mononuclear blood cells can now be attained. Future studies will tell whether technical progress in dialysis technique results in a decrease in the incidence of symptomatic dialysis-associated amyloidosis.

Occurrence of endotoxin in dialysis fluid from 39 dialysis units

Endotoxin exposure during haemodialysis may cause acute and chronic adverse reactions. In order to estimate the risk to the patient, samples of dialysis fluid from 39 of the 45 dialysis units in Sweden were analysed by the chromogenic Limulus amoebocyte lysate assay. Higher levels were obtained after the usual weekend shutdowns. The length of the tubing delivering the reverse osmosis water seemed to influence the extent of contamination. Fifty-nine percent of the units showed low mean endotoxin levels (i.e. mean concentration below the recommended limit in Sweden: < 25 ng l-1), while 18% of units had high levels (mean concentration > 100 ng l-1).