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Glucocorticoids are typically prescribed for the treatment of idiopathic nephrotic syndrome of childhood. In selected patients with refractory focal segmental glomuerulosclerosis (FSGS), adrenocorticotropin (ACTH) can be used to induce remission and decrease the progression of the disease. We report a 6 8/12-year-old girl with recurrent proteinuria, resistant to standard immunotherapy. She underwent related renal transplant but again developed proteinuria and was started on ACTH. She subsequently developed peripheral precocious puberty (PPP), presumably from peripheral aromatization of adrenal androgens. She was started on an aromatase inhibitor, and her ACTH dose was slowly decreased. She then developed central precocious puberty (CPP). We hypothesize that treatment of her peripheral precocious puberty with an aromatase inhibitor may have triggered central precocious puberty.

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A white girl presented at 8 months of age with thrombotic microangiopathy, followed by recurrent episodes of renal dysfunction, hemolysis, and thrombocytopenia, compatible with atypical hemolytic uremic syndrome. The episodes of the syndrome were treated by a combination of infusions of fresh frozen plasma, plasmapheresis, and continuous venovenous hemodialysis. Interval resolution occurred between episodes. At 2 years of age, prophylactic infusions of fresh frozen plasma were started between relapses, but this proved to be poorly protective; however, introduction of prophylactic intravenous gamma globulin at age 3.5 years resulted in prolonged remission (42 months). Serum levels of the third and fourth components of complement, total hemolytic complement, and complement factor H were normal. Results of the third component functional assay were low before and normalized after the start of immunoglobulin G prophylaxis. A missense mutation of complement factor H was identified. At 6 years of age, the patient underwent bilateral native nephrectomy and started long-term peritoneal dialysis, followed by a combined liver-kidney transplant at age 8 years. Four and a half years after transplant, she has excellent renal and liver graft function without recurrence of atypical hemolytic uremic syndrome.

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Nephrolithiasis is responsible for 1 in 1000 to 1 in 7600 pediatric hospital admissions annually throughout the United States. Seventy-five percent of children with nephrolithiasis have an identifiable predisposition to stone formation. This article reviews the different causes and disease states associated with nephrolithiasis in the pediatric population. The initial evaluation and the metabolic evaluation of children with nephrolithiasis are reviewed. Treatment modalities for the different stone types are also described.

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Exocytic insertion of H(+)-ATPase into the apical membrane of inner medullary collecting duct (IMCD) cells is dependent on a soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein target receptor (SNARE) complex. In this study we determined the role of Munc-18 in regulation of IMCD cell exocytosis of H(+)-ATPase. We compared the effect of acute cell acidification (the stimulus for IMCD exocytosis) on the interaction of syntaxin 1A with Munc-18-2 and the 31-kDa subunit of H(+)-ATPase. Immunoprecipitation revealed that cell acidification decreased green fluorescent protein (GFP)-syntaxin 1A and Munc-18-2 interaction by 49 +/- 7% and increased the interaction between GFP-syntaxin 1A and H(+)-ATPase by 170 +/- 23%. Apical membrane Munc-18-2 decreased by 27.5 +/- 4.6% and H(+)-ATPase increased by 246 +/- 22%, whereas GP-135, an apical membrane marker, did not increase. Pretreatment of IMCD cells with a PKC inhibitor (GO-6983) diminished the previously described changes in Munc-18-2-syntaxin 1A interaction and redistribution of H(+)-ATPase. In a pull-down assay of H(+)-ATPase by glutathione S-transferase (GST)-syntaxin 1A bound to beads, preincubation of beads with an approximately twofold excess of His-Munc-18-2 decreased H(+)-ATPase pulled down by 64 +/- 16%. IMCD cells that overexpress Munc-18-2 had a reduced rate of proton transport compared with control cells. We conclude that Munc-18-2 must dissociate from the syntaxin 1A protein for the exocytosis of H(+)-ATPase to occur. This dissociation leads to a conformational change in syntaxin 1A, allowing it to interact with H(+)-ATPase, synaptosome-associated protein (SNAP)-23, and vesicle-associated membrane protein (VAMP), forming the SNARE complex that leads to the docking and fusion of H(+)-ATPase vesicles.

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PURPOSE OF REVIEW: Research in the past several years has led to the understanding of numerous genetic mutations that lead to inheritable forms of distal renal tubular acidosis (dRTA). Most of these mutations affect the physiology of the A-intercalated cells of the renal cortical collecting duct. These include mutations of genes encoding carbonic anhydrase II, kidney anion exchanger 1, and different subunits of the H+-ATPase proton pump. Genetic defects in any one of these components may impair renal acidification and thereby result in persistent acidosis, failure to thrive, and nephrocalcinosis. RECENT FINDINGS: The present review provides a summary of the most recently identified genetic mutations resulting in a dRTA phenotype and, when possible, describes a mechanism. Most causes of dRTA are due to loss of function or inappropriate targeting of transporters. SUMMARY: The collaboration of clinicians, geneticists, and renal physiologists has enabled us to better understand at the cellular level the different mechanisms leading to dRTA. Such information should lead to earlier diagnosis and treatment, thereby minimizing the irreversible complications affecting patients with this or similar diseases.

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