Geneviève Guest

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.

Genetic and Functional Analyses of Membrane Cofactor Protein (CD46) Mutations in Atypical Hemolytic Uremic Syndrome

Hemolytic uremic syndrome (HUS) is characterized by the triad of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. The non-Shiga toxin-associated HUS (atypical HUS [aHUS]) has been shown to be a disease of complement dysregulation. Mutations in the plasma complement regulators factor H and factor I and the widely expressed membrane cofactor protein (MCP; CD46) have been described recently. This study looked for MCP mutations in a panel of 120 patients with aHUS. In this cohort, approximately 10% of patients with aHUS (11 patients; nine pedigrees) have mutations in MCP. The onset typically was in early childhood. Unlike patients with factor I or factor H mutations, most of the patients do not develop end-stage renal failure after aHUS. The majority of patients have a mutation that causes reduced MCP surface expression. A small proportion expressed normal levels of a dysfunctional protein. As in other studies, incomplete penetrance is shown, suggesting that MCP is a predisposing factor rather than a direct causal factor. The low level of recurrence of aHUS in transplantation in patients with MCP mutations is confirmed, and the first MCP null individuals are described. This study confirms the association between MCP deficiency and aHUS and further establishes that a deficiency in complement regulation, specifically cofactor activity, predisposes to severe thrombotic microangiopathy in the renal vasculature.

Cysteamine therapy delays the progression of nephropathic cystinosis in late adolescents and adults.

Nephropathic cystinosis is a multisystem autosomal recessive disease caused by cystine accumulation, which is usually treated by oral cysteamine. In order to determine long-term effects of this therapy, we enrolled 86 adult patients (mean age 26.7 years) diagnosed with nephropathic cystinosis, 75 of whom received cysteamine. Therapy was initiated at a mean age of 9.9 years with a mean duration of 17.4 years. By last follow-up, 78 patients had end-stage renal disease (mean age 11.1 years), 62 had hypothyroidism (mean age 13.4), 48 developed diabetes (mean age 17.1 years), and 32 had neuromuscular disorders (mean age 23.3 years). Initiating cysteamine therapy before 5 years of age significantly decreased the incidence and delayed the onset of end-stage renal disease, and significantly delayed the onset of hypothyroidism, diabetes, and neuromuscular disorders. The development of diabetes and hypothyroidism was still significantly delayed, however, in patients in whom therapy was initiated after 5 years of age, compared with untreated patients. The life expectancy was significantly improved in cysteamine-treated versus untreated patients. Thus, cysteamine decreases and delays the onset of complications and improves life expectancy in cystinosis. Hence, cysteamine therapy should be introduced as early as possible during childhood and maintained lifelong.

Long term results of liver-kidney transplantation in children with primary hyperoxaluria.

Abstract. From 1990 to 2000, we performed eight liver-kidney transplants in eight children, aged 1–16 years, with end-stage renal failure (ESRF) due to primary hyperoxaluria (PH1). The duration of dialysis before transplantation ranged from 2 to 42 months (mean 14 months) and was <1 year in four patients. Only the first patient underwent postoperative hemodialysis; in the other five, we chose to induce maximal diuresis from the first hours with intravenous and intragastric hyperhydration (≥3 l/m2 per day). High water intake with nocturnal tube hydration was maintained for 6 months to 5 years, as long as oxaluria exceeded 0.5 mmol/day. A quadruple sequential immunosuppressive regimen was used. Two patients died during liver graft surgery. The other six patients are alive and well, with a mean follow-up of 7.4 years (range 5–11 years). Patient and graft survival is 75% at 5 years. At latest follow-up, liver tests were normal in all six patients; creatinine clearance ranged from 55 to 95 ml/min per 1.73 m2 (mean=74). Oxaluria was lower than 0.4 mmol/day in all patients (mean=0.22). The six patients underwent 15 renal biopsies, 1–11 years after transplantation. Chronic transplant nephropathy was present in four patients and mild cyclosporin nephrotoxicity in another. No oxalate crystals were seen and repeat ultrasonography has been consistently normal in all patients. The three patients with bone oxalosis showed progressive complete healing of bone lesions. All six children or adolescents now live a normal life. From this series, we conclude that early combined liver-kidney transplantation is the treatment of choice for children with ESRF due to primary hyperoxaluria.

Hypertension following renal transplantation in children

The files of 334 consecutive cadaver kidney (CK) and of 27 living related (LR) transplantations (T) in children and adolescents performed from 1973 to 1984 have been reviewed. Following cadaver transplantation, 52 patients (15%) never had hypertension (HT), 41 patients (12%) had only initial HT up to 6 months after transplantation and 18 other patients (5%) exhibited transient HT episodes while on high-dose steroid therapy. Finally, 209 patients (62%) had HT for periods longer than 6 months and 16 patients (5%) until death or graft failure within the first 3 months. Chronic graft rejection was the major cause of HT, but other factors either isolated or in association were also present. Renal artery stenosis (RAS) was diagnosed in 43 cases (13%) 2–17 months post-transplantation; 10 of these were operated upon (5 successfully) and 9 underwent transluminal angioplasty with a single success. Nine cases of RAS resolved spontaneously. HT was attributed to the host kidney in 10 cases (3%) and to recurrence of primary renal disease in 9 (3%). HT observed after CKT was sometimes severe and difficult to control. Acute complications from HT were recorded in 35 cases, with 6 deaths and 2 severe neurological sequelae. Among 25 LRT, 11 cases (40%) had no HT 13 (48%) had HT for longer than 6 months. In this group, no case of RAS was observed and only one complication (without sequelae) was noted. In conclusion, HT is a frequent and sometimes severe complication post-transplantation in children and adolescents.

Deletion of mitochondrial DNA in patient with chronic tubulointerstitial nephritis.

We report a mitochondrial DNA deletion (2.6 kb) in a boy with tubulointerstitial nephritis in whom chronic renal failure and leukodystrophy subsequently developed. Elevated lactate values in plasma and cerebrospinal fluid were suggestive of a defect in the mitochondrial respiratory chain. High amounts of deleted mitochondrial DNA were present in muscle and cerebral white matter. On the basis of this observation, we suggest giving consideration to genetic defects of oxidative phosphorylation in any attempt to determine the origin of unexplained chronic tubulointerstitial nephritis, especially when seemingly unrelated organs are involved.

In Vivo Confocal Microscopy and Anterior Segment Optical Coherence Tomography Analysis of the Cornea in Nephropathic Cystinosis

OBJECTIVE To analyze the corneas of patients with nephropathic cystinosis using in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT). DESIGN Prospective case series. PARTICIPANTS Sixteen eyes of 8 patients with nephropathic cystinosis aged 8 to 21 years. METHODS The ophthalmologic evaluation included best-corrected visual acuity, evaluation of photophobia (0-4), slit-lamp biomicroscopy analysis, intraocular pressure measurement, evaluation of crystal density using a slit-lamp-based scoring of the cornea, as well as AS-OCT and IVCM analysis. MAIN OUTCOME MEASURES The depth of crystal deposition (DCD) in the central cornea and the central cornea thickness (CCT) were assessed using AS-OCT and IVCM. The IVCM images were evaluated for crystal density in each corneal layer and an IVCM score was calculated for each eye. RESULTS All eyes had corneal crystal deposits, with a mean slit-lamp photography score of 2.90+/-0.13 (range, 2.75-3.00). Using AS-OCT, corneal crystals were observed in all eyes. These crystals appeared as hyperreflective punctuate deposits, predominantly observed within the anterior stroma. Measured with AS-OCT, the mean depth of DCD in the central cornea was 291.40+/-81.42 microm (range, 200-531 microm); the mean CCT was 543.47+/-29.62 microm. Using IVCM, the crystals appeared as spindle, needle-shaped, and fusiform hyperreflective bodies measuring from 1 to 175 microm in length and 1 to 30 microm in thickness. Except for the endothelium, randomly oriented crystals were observed in all corneal layers, with the greatest density observed within the anterior stroma. Measured with IVCM, the mean DCD was 426.07+/-88.19 microm (range, 284-531 microm); the mean CCT was 531.87+/-34.77 microm. There was no significant difference between the CCT measurements obtained with IVCM and with AS-OCT (mean difference, 11.31 microm; P = 0.07). Nevertheless, the DCD was significantly higher with IVCM than with AS-OCT (mean difference, 126.25 microm; P<0.0001). CONCLUSIONS In patients with nephropathic cystinosis, IVCM could precisely quantify the density of crystals within the central cornea. Anterior segment OCT and IVCM should be used in further studies evaluating crystal deposition in patients with nephropathic cystinosis. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

ROLE OF THE BLADDER IN DELAYED FAILURE OF KIDNEY TRANSPLANTS IN BOYS WITH POSTERIOR URETHRAL VALVES

PURPOSE There is a tendency toward less favorable long-term graft function in patients with posterior urethral valves than in controls. We studied the role of the bladder in boys who underwent transplantation by simultaneously evaluating renal graft and voiding function. MATERIALS AND METHODS Between 1972 and 1994, 66 boys with posterior urethral valves underwent kidney transplantation. Of these boys 44 with a mean age of 9.7 years who retained a functional renal graft did not undergo any surgery on the lower urinary tract except for the initial treatment of posterior urethral valves. Long-term evaluation included a voiding questionnaire, radiological assessment and serum creatinine measurement. RESULTS Average followup was 9.01 years (range 2.4 to 19.6). There was no voiding dysfunction symptomatology in 23 boys, while 3 (14.2%) and 8 (38.1%) of the remaining 21 had daytime and nighttime frequency, respectively. Dysuria and incontinence were present in 11 (52.4%) and 12 (57.1%) patients, respectively. Urodynamics in 11 cases revealed a mean bladder compliance plus or minus standard deviation of 11.3+/-2.8 ml./cm. water. In boys with a voiding disorder mean serum creatinine increased after 5 years of followup. At 10 years after kidney transplantation mean serum creatinine was 140.3+/-36.0 and 285.7+/-36.2 micromol./l. in asymptomatic boys and those with a voiding disorder, respectively (p<0.01). CONCLUSIONS Valve bladder has a role in the deterioration of renal transplants in boys with posterior urethral valves. In those with a voiding disorder closer followup is needed, including urodynamic and radiological studies. Bladder dysfunction, such as hypocompliance and/or hyperreflexia, requires medical or surgical treatment.

A controlled study of deflazacort in the treatment of idiopathic nephrotic syndrome

Abstract.Forty patients with steroid-dependent idiopathic nephrotic syndrome (INS), a mean follow-up of 5.5 years, and a mean number of relapses of ten were blindly assigned to either deflazacort (DFZ) (n = 20) or prednisone (PDN) (n = 20) according to a ratio of equivalence of DFZ/PDN = 0.8. This treatment was given for 1 year. The number of relapses was significantly lower in patients receiving DFZ. After 1 year, 12 remained in remission with DFZ compared with 2 with PDN. Growth velocity was not different in the two groups. Bone mineral content, assessed by quantitative computed tomography of L1 L2 vertebrae, decreased after 1 year by 6% in the DFZ group versus 12% in the PDN group (NS). The mean body weight increase of +3.9±4.1 kg in the PDN group was higher than that of the DFZ group, +1.7±2.8 kg (P = 0.06). Cushingoid symptoms tended to be less after 12 months in the DFZ group. In conclusion, this study shows that DFZ was more effective than PDN in limiting relapses in steroid-dependent INS, and that cushingoid symptoms, weight gain, and decrease in bone mineral content tended to be less marked with this drug than with PDN.

Familial Hypomagnesemia with Hypercalciuria and Nephrocalcinosis: Phenotype–Genotype Correlation and Outcome in 32 Patients with CLDN16 or CLDN19 Mutations

BACKGROUND AND OBJECTIVES Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is a rare autosomal recessive renal tubular disease. It is caused by mutations in CLDN16 and CLDN19, encoding claudin-16 and -19, respectively. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is usually complicated by progressive CKD. The objectives of this study were to describe the clinical and genetic features of familial hypomagnesemia with hypercalciuria and nephrocalcinosis and analyze phenotype-genotype associations in patients with CLDN16 or CLDN19 mutations. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Data from 32 genetically confirmed patients (9 patients with CLDN16 and 23 patients with CLDN19 mutations) from 26 unrelated families were retrospectively reviewed. RESULTS Diagnosis was based on clinical criteria at a median age of 9.5 years and confirmed by genetic testing at a median age of 15.5 years. In total, 13 CLDN16 or CLDN19 mutations were identified, including 8 novel mutations. A founder effect was detected for the recurrent CLDN16 p.Ala139Val mutation in North African families and the CLDN19 p.Gly20Asp mutation in Spanish and French families. CKD was more frequently observed in patients with CLDN19 mutations: survival without CKD or ESRD was 56% at 20 years of age in CLDN19 versus 100% in CLDN16 mutations (log rank P<0.01). Ocular abnormalities were observed in 91% of patients with CLDN19 mutations and none of the patients with CLDN16 mutations (P<0.01). Treatments seem to have no effect on hypercalciuria and CKD progression. CONCLUSIONS Patients with CLDN19 mutations may display more severe renal impairment than patients with CLDN16 mutations. Ocular abnormalities were observed only in patients with CLDN19 mutations.