Bernard Boudailliez

Differential Impact of Complement Mutations on Clinical Characteristics in Atypical Hemolytic Uremic Syndrome

Mutations in factor H (CFH), factor I (IF), and membrane cofactor protein (MCP) genes have been described as risk factors for atypical hemolytic uremic syndrome (aHUS). This study analyzed the impact of complement mutations on the outcome of 46 children with aHUS. A total of 52% of patients had mutations in one or two of known susceptibility factors (22, 13, and 15% of patients with CFH, IF, or MCP mutations, respectively; 2% with CFH+IF mutations). Age <3 mo at onset seems to be characteristic of CFH and IF mutation-associated aHUS. The most severe prognosis was in the CFH mutation group, 60% of whom reached ESRD or died within <1 yr. Only 30% of CFH mutations were localized in SCR20. MCP mutation-associated HUS has a relapsing course, but none of the children reached ESRD at 1 yr. Half of patients with IF mutation had a rapid evolution to ESRD, and half recovered. Plasmatherapy seemed to have a beneficial effect in one third of patients from all groups except for the MCP mutation group. Only eight (33%) of 24 kidney transplantations that were performed in 15 patients were successful. Graft failures were due to early graft thrombosis (50%) or HUS recurrence. In conclusion, outcome of HUS in patients with CFH mutation is catastrophic, and posttransplantation outcome is poor in all groups except for the MCP mutation group. New therapies are urgently needed, and further research should elucidate the unexplained HUS group.

Disappearance of Aluminic Bone Disease in a Long Term Asymptomatic Dialysis Population Restricting Al(OH)3 Intake: Emergence of an Idiopathic Adynamic Bone Disease Not Related to Aluminum

In dialysis centers using reverse osmosis-treated water but not restricting A1(OH)3 administration, a high prevalence of histological aluminum bone disease has been reported. To assess whether this is also the case in our center where A1(OH)3 intake has always been restricted and even completely given up after 1980 thanks to high doses of CaCO3, we reviewed 42 bone biopsies performed between 1975 and 1985 in patients dialyzed for a mean duration of 56 months. Seventeen of these patients had been dialyzed before 1978 with softened water moderately contamined by aluminum, 15 had always been dialyzed with reverse osmosis-treated water and 10 had been exclusively treated by hemofiltration. The prevalence of aluminum bone disease in the whole population was 9.5% (4 patients) and consisted only of adynamic bone disease, osteomalacia being totally absent. When the patients dialyzed with aluminum-contaminated water were excluded as well as 1 diabetic patient who had taken A1(OH)3 for 1.5 years the prevalence of aluminum bone disease was null in this population. When the whole population is considered the prevalence of the other types of bone disease was 76% for osteitis fibrosa and 14.5% for a non-aluminic adynamic bone disease (6 cases). These latter cases differed from the osteitis fibrosa group only by a relative hypoparathyroidism not explained by higher plasma concentrations and higher oral cumulative doses of calcium, magnesium and aluminum or by lower plasma concentrations of phosphate and bicarbonate. None had previous parathyroidectomy, one had an unsuccessful transplantation and one was diabetic. Iron overload was excluded by negative Perls staining.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of conservative treatment on the renal outcome of children with primary hyperoxaluria type 1

Primary hyperoxaluria type 1 results from alanine:glyoxylate aminotransferase deficiency. Due to genotype/phenotype heterogeneity in this autosomal recessive disorder, the renal outcome is difficult to predict in these patients and the long-term impact of conservative management in children is unknown. We report here a multicenter retrospective study on the renal outcome in 27 affected children whose biological diagnosis was based on either decreased enzyme activity or identification of mutations in the patient or his siblings. The median age at first symptoms was 2.4 years while that at initiation of conservative treatment was 4.1 years; 6 children were diagnosed upon family screening. The median follow-up was 8.7 years. At diagnosis, 15 patients had an estimated glomerular filtration rate (eGFR) below 90, and 7 children already had stage 2-3 chronic kidney disease. The median baseline eGFR was 74, which rose to 114 with management in the 22 patients who did not require renal replacement therapy. Overall, 20 patients had a stable eGFR, however, 7 exhibited a decline in eGFR of over 20 during the study period. In a Cox regression model, the only variable significantly associated with deterioration of renal function was therapeutic delay with a relative risk of 1.7 per year. Our study strongly suggests that early and aggressive conservative management may preserve renal function of compliant children with this disorder, thereby avoiding dialysis and postponing transplantation.

Effect of Hydrochlorothiazide on Urinary Calcium Excretion in Dent Disease: An Uncontrolled Trial

BACKGROUND Thiazide doses equivalent to 1 to 2 mg/kg/d of hydrochlorothiazide (HCTZ) have been proposed to correct hypercalciuria and prevent kidney failure in patients with Dent disease. However, they can cause adverse metabolic effects in the long term. In treating hypertension in children, lower thiazide doses have been shown to be as effective and well tolerated. STUDY DESIGN Uncontrolled trial, with forced-titration sequential open-label study design. SETTING & PARTICIPANTS 7 boys with genetically confirmed Dent disease and mild phenotype (neither overt sodium wasting nor kidney failure). INTERVENTION After a 1-month run-in period, patients sequentially received amiloride (5 mg/d) alone (1 month) and then for 3 periods of 2 months in association with increasing doses of HCTZ (<0.2, 0.2 to 0.4, and 0.4 to 0.8 mg/kg/d). OUTCOMES Urinary calcium excretion and extracellular volume indicators. MEASUREMENTS At the end of each period, 2 daily 24-hour urinary collections were performed on the days preceding admission. Blood and spot urine samples also were collected. RESULTS A greater HCTZ dose increased renin, aldosterone, and plasma protein concentrations. Amiloride alone had no effect on calcium excretion. The greatest HCTZ doses decreased spot urinary calcium excretion by 42% compared with baseline (median, 0.3; minimum, maximum, 0.2, 0.8 versus median, 0.8; minimum, maximum, 0.4, 1.1, respectively; P = 0.03). However, patients developed adverse reactions, including muscle cramps (n = 2), biological (n = 7) or symptomatic hypovolemia (n = 1), hypokalemia (n = 4), and hyponatremia (n = 1), which all corrected after treatment withdrawal. LIMITATION Small sample size and absence of a control group. CONCLUSION HCTZ doses greater than 0.4 mg/kg/d decreased calcium excretion, but were associated with significant adverse events. Thiazide diuretic therapy should be considered with caution in children with Dent disease.

Control of Predialytic Hyperphosphatemia by Oral Calcium Acetate and Calcium Carbonate

Since Mai et al. found, with the intestinal lavage technique, that the same dose of elemental calcium given as acetate (Ca Ac) complexed in the gut of uremic patients twice as much phosphate as calcium carbonate (CaCO3) while inducing a rather low calcium absorption, we wanted to see if half the dose of elemental calcium given as Ca Ac could control, on medium term, the predialysis plasma phosphate as well as CaCO3 while inducing less frequent hypercalcemia. This was evaluated in a cross-over study of 3 periods of 10 weeks according to the sequence Ca Ac, CaCO3 and Ca Ac, in 12 compliant patients on chronic dialysis previously treated by CaCO3. Because of poor tolerance of Ca Ac during the first period, 4 patients were excluded and the results were assessed only on the 8 patients who completed the study. For half the doses of elemental calcium (620 +/- 250 mg versus 1,310 +/- 560 mg versus 710 +/- 200 mg/day), Ca Ac allowed the same control of predialytic hyperphosphatemia (1.67 +/- 0.34; 1.74 +/- 0.32; 1.75 +/- 0.38) with paradoxically comparable normal mean plasma calcium concentration (2.61 +/- 0.14; 2.56 +/- 0.13; 2.55 +/- 0.14 mmol/l). Plasma alkaline phosphatases and intact PTH concentrations remained also stable during the 3 periods. The frequency of hypercalcemia greater than 2.75 mmol/l (12; 9; 20%) and of hyperphosphatemia greater than 2 mmol/l (17; 22; 27%) were comparable with the 2 treatments. In conclusion, Ca Ac controls predialytic hyperphosphatemia as efficiently as CaCO3 for half the dose of elemental calcium without, however, decreasing the frequency of hypercalcemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Leukaemia-associated hypercalcaemia in a 10-year-old boy: effectiveness of aminohydroxypropylidene biphosphonate

A 10-year-old boy with leukaemia-associated hypercalcaemia was treated with aminohydroxypropylidene biphosphonate (AHPrBP previously APD) in a total dosage of 60 mg over 5 days, when the condition failed to respond to rehydration and frusemide and no sustained effect was produced by haemodialysis with a calcium (Ca)-free dialysate. Bone films showed no lytic lesions, and AHPrBP, which is a potent inhibitor of osteoclast-mediated bone resorption was well tolerated and induced a rapid and sustained fall in plasma Ca (from 3.42 to 2.07 mM in 5 days). Plasma magnesium and alkaline phosphatase remained normal. The results could have been affected by other drugs [vincristine, cyclophosphamide, zorubicin (Rubidazone)l-asparaginase and prednisone] which were simultaneously administered. However, the observation that: (1) the response curve of plasma Ca was similar to that reported when AHPrBP was used alone, (2) there was complete inhibition of urinary Ca excretion and (3) hypocalcaemia occurred suggests that AHPrBP was the major cause of the reduction in plasma Ca. AHPrBP should be considered a potential therapy for hypercalcaemia in childhood malignancy.

Prevention of hyperparathyroidism in patients on maintenance dialysis by intravenous 1-alpha-hydroxyvitamin D3 in association with Mg(OH)2 as sole phosphate binder : a randomized comparative study with the association CaCO3±Mg(OH)2

The purpose of this study is to evaluate the place of intravenous 1 alpha-hydroxyvitamin D3 (1 alpha-OH-D3) in the prevention of radiologically obvious hyperparathyroidism (HPT) in patients on maintenance dialysis while excluding aluminium phosphate binder and using a dialysate calcium concentration of 1.62 mmol which keeps the intradialytic calcium balance neutral. Therefore, 47 patients without subperiosteal resorption and previously treated by oral CaCO3 and if necessary Mg(OH)2 as phosphate binder while their dialysate calcium had a Ca level of 1.62 and a Mg level of 0.2 mmol/l were randomized into a control group of 24 who were maintained on the same treatment and an experimental group of 23. This group discontinued CaCO3 and received intravenous 1 alpha-OH-D3 after each dialysis at increasing doses up to 4 micrograms and increased Mg(OH)2 as their sole phosphate binder. When plasma Ca increased above 2.7 mmol/l, the dose of 1 alpha-OH-D3 was decreased. When plasma PO4 increased above 2 mmol/l, the dose of Mg(OH)2 was increased to the highest dose not inducing diarrhea, hypermagnesemia (less than 2 mmol/l) or hyperkalemia (less than 6 mmol/l). In case of persistent hyperphosphatemia, the dose of 1 alpha-OH-D3 was decreased. Since mean plasma alkaline phosphatase was normal, HPT was monitored on the plasma concentration of 1-84 PTH for which a previous histological study showed that frank osteitis fibrosa was present only when they were above 70 pg/ml, i.e. (about twice the upper limit of the normal value). Before the study, plasma PTH was below this limit in 16 patients of the CaCO3 group and in 14 patients of the 1 alpha-OH-D3 group. After 6 months, they remained below this limit in all patients except 2 of each group. Plasma PTH was initially above 70 pg/ml in 8 of the CaCO3 and did not change significantly throughout the study, 2 patients having at 6 months a PTH level below 70 pg/ml. In contrast with intravenous 1 alpha-OH-D3, all the 9 patients with initial frank HPT decreased their PTH levels after 2 months, the levels being below 70 pg/ml in 6 cases. However, because of hypercalcemia and/or of hyperphosphatemia in spite of a highest tolerable dose of Mg(OH)2, 1 alpha-OH-D3 doses had to be decreased down to 0.4 microgram per dialysis at the 6th month so that at 6 months 6 of 9 patients had their PTH levels above 70 pg/ml, a number comparable to that of patients treated with CaCO3 (6 of 8).(ABSTRACT TRUNCATED AT 400 WORDS)

Idiopathic Hypercalciuria: Proposal for a New Cascade

Idiopathic hypercalciuria (IH) is defined by a 24 hour urinary excretion of calcium greater than 4 mg or 0.1 mmol/kg of body weight on a calcium diet of 1 g and greater than 3 mg or 0.07 mmol/kg on a Ca diet of 400 mg, while there is no excess of sodium (120–180 mmol) nor of protein (1–1.3 g/kg per day). IH with fasting hypercalciuria but without secondary hyperparathyroidism represents in our experiece the most prevalent subtype of IH. Since bone mineral density has been shown to be decreased in this undetermined subtype (Pak’s classification), as in patients with absorptive hypercalciuria type I or with renal hypercalciuria, the clinical relevance of this classification is questioned. A primary bone hyperresorption seems to be the main explanation of IH, since in this group as a whole, fasting hypercalciuria is correlated positively with fasting hydroxyprolinuria which is higher than in controls. This bone resorption may be favored by protein intake of non-dairy origin due to a higher meat intake and hypersensitivity of bone resorption to meat intake, as evidenced by a higher daily urinary excretion of urea on a diet without dairy products and a steeper slope of the regression of fasting calciuria versus 24 hour urea excretion. Furthermore, calcitriol synthesis is increased, probably because of a hypersensitivity of 25 OH vitamin D 1α hydroxylase to phosphate, as evidenced by the fact that plasma calcitriol correlates negatively with plasma phosphate which, however, remains in the normal range. High plasma calcitriol is not responsible for the bone hyperresorption, since it correlates negatively with fasting hypercalciuria and positively with bone density and postprandial calciuria (an index of calcium absorption).

Recent Advances in the Treatment of Renal Osteodystrophy

Renal osteodystrophy becomes clinically significant when the following features are present: clinical symptoms (pain, muscle weakness, pruritus), radiological signs (subperiosteal erosions, osteopenia, fractures or pseudofractures, slipped epiphysis with coxa vara or genu valgum in children, metastatic calcification) and marked plasma abnormalities, particularly uncontrollable hyperphosphatemia. Clinically significant bone disease is not usually seen in adults until they have been on dialysis for several years but may be seen earlier (even before dialysis has been started) in children. Such bone disease may be due either to hyperparathyroidism or to aluminum (Al) bone disease. In favor of hyperparathyroidism are the following features (1, 2): rarity of pain and fractures, greater elevation of alkaline phosphatase, greater elevation of parathyroid hormone (PTH) plasma concentration and lower basal plasma concentration of Al (<300 µg/l) with smaller increase of plasma Al after i.v. administration of desferoxamine (increase <175 µg/l). It is only by bone biopsy, however, that it is possible to differentiate with certainty osteitis fibrosa, the bone expression of hyperparathyroidism, from osteomalacia or adynamic bone disease, both of which have been linked to Al intoxication (1, 2).

Alternative phosphate binders for aluminium hydroxide

In this chapter, we discuss the use of high doses of CaC03 and other alkaline salts of calcium as well as of magnesium hydroxide and magnesium carbonate as alternative phosphate binders for Al(OH)2.