Genotype/phenotype observations in African Americans with Bartter syndrome.

BACKGROUND: Two Bartter syndrome phenotypes have been described, and molecular analyses demonstrate mutations in 1 of 3 genes encoding ascending limb of Henle transporters. We report phenotypic observations in 5 African American children with Bartter syndrome in the context of a distinct genotype. METHODS: Mutation analyses were performed in 5 unrelated African American children with Bartter syndrome. These results were correlated to clinical and laboratory data. Calcium metabolism was evaluated with a bone disk bioassay. RESULTS: Mutation analyses demonstrated homozygous deletion of the ClC-Kb gene in all children. Two children had polyhydramnios and premature birth; the others were born at term and presented with failure to thrive or dehydration. All receive indomethacin, spironolactone, and potassium chloride with improved but borderline hypokalemia. Growth has improved with therapy, but height SD scores range from -3.9- to -1.4. Urinary calcium excretion is normal, and bone disk bioassay shows no abnormal calciotropic activity. No patient had nephrocalcinosis, but renal sonograms show loss of corticomedullary differentiation. CONCLUSIONS: African Americans with Bartter syndrome genotyped to date have homozygous deletion of ClC-Kb Clinical observations in our patients include partial correction of hypokalemia and suboptimal growth despite therapy. Abnormal calciotropic activity and nephrocalcinosis are not seen, but renal ultrasounds are abnormal.

Center volume effects in pediatric renal transplantation. A report of the North American Pediatric Renal Transplant Cooperative Study.

An inverse relationship between mortality and center volume has been established for several surgical procedures. Given the distinctiveness of pediatric renal transplantation and the large variation in center volume, investigation for relationships between center volume and graft outcome was pursued using the North American Pediatric Transplant Cooperative Study database. Center volume groups were based on the total number of pediatric transplants reported from 1987 to 1995. Centers reporting > 100, 51-100, or < or = 50 transplants were grouped as high- (n=11), moderate- (n=28), or low-volume (n=65), respectively. Differences between groups included increasing rates of cadaver donor graft thrombosis (2.4%, 4.3%, and 5.7%, P<0.01) and acute tubular necrosis (ATN) (10.2%, 11.5%, and 14.0%, P<0.01) with decreasing center volume. Treatment differences included a higher rate of induction with an anti-T-cell antibody preparation in the larger-volume groups, 60.2%, 51.8%, and 39.2% (P<0.001). Decreasing graft survival for decreasing center size groups was noted at 3 months post transplant, 90.4%, 90.2%, and 88.4%. These differences were significant only with the exclusion of anti-T-cell induction from the proportional hazards model (relative risk=0.81 and =0.70 for the moderate- and high-volume groups, P<0.02). Superior graft survival in the high-volume centers noted at 3 months post transplant appears predominantly the result of lower rates of cadaver donor graft thrombosis and ATN. Analysis points to the need for low-volume centers to identify risk factors influencing these outcomes.

Tubulointerstitial nephritis induced by the leukotriene receptor antagonist pranlukast.

A 7-year-old boy with asthma was receiving the leukotriene receptor antagonist pranlukast (Ultair; SmithKline Beecham; Pittsburgh) as part of an open-label clinical trial. The patient's asthma improved, and he remained asymptomatic; but routine study evaluations 9 to 12 months into therapy showed microhematuria, proteinuria, glucosuria, anemia, and renal insufficiency. Renal biopsy demonstrated changes classic for acute allergic tubulointerstitial nephritis (ATIN), with mixed interstitial inflammatory infiltrate including eosinophils. Within 6 months of pranlukast withdrawal, anemia resolved and urinary sediment and renal function normalized. The case demonstrates that hypersensitivity reaction to pranlukast and resultant ATIN is possible, and that periodic urine testing in patients receiving pranlukast should be considered.

Plasma creatinine results derived from an endpoint modification of the Jaffé method.

For values in the normal pediatric range, endpoint modifications of the Jaffé method for measuring plasma creatinine (PCr) yield higher results than other commonly used techniques. In an effort to evaluate the Olympus AU5000 endpoint method used by the large reference laboratory to which many of our patients are directed by their third-party payor, we compared results with a kinetic Jaffé technique using paired samples from the same specimens. In 46 samples, the kinetic method measured Pcr at < or =0.8 mg/dl, whereas the endpoint technique PCr was higher by 0.1 mg/dl in 6 (13%), 0.2 mg/dl in 23 (50%), and 0.3 mg/dl in 16 (35%) samples (P<0.0001). The combination of these higher values and the same reported normal range for all children ages 2-12 years (0.3-1.0 mg/dl) and 13-17 years (0.7-1.4 mg/dl) makes interpretation of Olympus AU5000 endpoint method results difficult, particularly for younger children. The results reinforce the need for each laboratory to provide comprehensive age- and sex-adjusted normal PCr ranges.

The utility of renin profiling in childhood hypertension.

Criteria to categorize children as having hypertension associated with high, low or normal PRA as determined by the technique of renin sodium indexing; or with PRA responsiveness which was normal, suppressed or excessive after acute volume depletion induced by a loop diuretic were established in 30 normotensive adolescents. Four hour upright PRA corrected for daily sodium excretion was elevated in 16% of 43 and 84% of 25 children with essential and renal related hypertension. Low PRA was found in 5 of 43 and 0 of 25 children. In 36 children with essential hypertension evaluated after acute volume depletion, 4 and 5 had hyper- and hypo- responsive PRA compared to the 30 normotensive children. The application of these two approaches enables the renin angiotensin system to be systematically categorized in hypertensive children.

Development of pneumatosis cystoides intestinalis following transperitoneal renal transplantation in a child.

A 9 1/2-year-old female developed pneumatosis cystoides intestinalis (PCI) which was detected radiographically 4 1/2 months after transperitoneal cadaveric renal transplantation, during a period characterized by recurrent episodes of acute rejection. Radiographic evaluation was prompted by the development of cramping abdominal pain, distention, and tenderness localized to the region of the allograft, which occurred during one such episode. Pneumatosis was localized primarily to an area of colon that lay in direct contact with the allograft. Evaluation of the available clinical and roentgenographic evidence suggested that pneumatosis may have resulted from the development of a sympathetic inflammatory reaction within the bowel wall adjacent to the acutely inflamed allograft. Subsequent stabilization of renal function was associated with resolution of the pneumatosis over the ensuing 8 months without surgical intervention or additional medical therapy.

Transperitoneal solute movement in children.

The transperitoneal movement of solute in children was examined by means of a theoretical consideration of the peritoneal clearance formula and by the performance of peritoneal solute diffusion curves and measurement of peritoneal clearances of multiple solutes. Theoretical considerations led to the conclusion that when dialysis mechanics are held constant, peritoneal clearances scaled for weight are similar in individuals of widely varying weight when the volume of infused dialysate is also scaled for weight if peritoneal permeability and surface area are constant. In one group of studies, solute diffusion curves and weight-scaled peritoneal clearances of urea, phosphate, creatinine, and urate were similar in 3 children ages 4 to 18 months compared to 4 children ages 2.5 to 18.5 years. In a second group of studies, weight-scaled peritoneal clearances of inulin but not urea were shown to be marginally lower in 4 children who had been dialyzed longer than 6 months compared with 4 children dialyzed less than 1 month. Hypertonic glucose dialysis in these children was shown to enhance urea clearance but not that of inulin. It is concluded that comparative studies of peritoneal clearances can characterize the transperitoneal movement of solute in children of widely varying body size. Such studies are of greatest value when systematically performed and similar ratios of dialysate volumes to body pools of solute are used.