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A 4-year-old boy was referred to the nephrologist with daytime urinary incontinence and suspicion of an overactive bladder. At the age of 17 months he had been referred to the pediatric endocrinologist because of polyuria and polydipsia in order to exclude diabetes insipidus. Repeated water deprivation tests and a magnetic resonance imaging scan of the brain were normal. Diabetes insipidus was excluded, and primary polydipsia was thought to be most likely since diabetes mellitus also had been excluded. At the current presentation, he drank up to 3 L a day and quite often had wet diapers. He also seemed to pass stools infrequently and with difficulty. Curiously his grandmother had similar symptoms of polyuria and polydipsia since childhood and had been diagnosed with primary polydipsia. The physical examination of our pediatric patient was normal. In the differential diagnosis we included diabetes insipidus but also contemplated other possibilities, such as nephronophthisis, tubulopathies and hypercalciuria. Laboratory results including urinalysis and an ultrasound of the kidney did not show any abnormalities, making a tubulopathy or hypercalciuria unlikely. A desmopressin test by the intravenous route came back completely normal, pointing to another cause than diabetes insipidus. Genetic testing for the nephronophthisis came back negative but was positive for a missense mutation in the AVPR2 gene (p.Arg104Cys) associated with partial nephrogenic diabetes insipidus. He was started on daily desmopressin. Within 3 days the urinary incontinence resolved as did the polyuria and faecal incontinence. His grandmother was referred to the geneticist and eventually the adult nephrologist. This case highlights the importance of being thorough when confronted with a difficult diagnosis. It also emphasizes that a test result does not necessarily equate to the presence or absence of a condition since the test with 100 % sensitivity and specificity has yet to be discovered.

The objective of this study was to investigate whether DNA polymorphisms of the renin-angiotensin system (RAS) genes were associated with renal scar formation in pediatric patients with bladder dysfunction (BD). Although these children are born healthy, due to persistence of immature voiding habits and evolution of BD, some develop progressive renal damage. It has been suggested that the DD genotype of the angiotensin I-converting enzyme (ACE) gene might be an adverse renal prognostic factor. The insertion/deletion (I/D) polymorphism of the ACE gene and the A1166C polymorphism of the angiotensin II type 1 receptor (ATR1) gene were identified by polymerase chain reaction amplification in 42 children with BD (aged 5-14 years) and 198 healthy adult controls. Twelve children had urgency syndrome and 30 had dysfunctional voiding. Renal scarring was found in 16 patients, while 26 patients had normal kidneys on dimercaptosuccinic acid scan. In children with renal lesions there was significant over-representation of the DD genotype compared with either controls or patients without renal damage ( P<0.05). On multivariate analysis, the DD genotype was the only factor that had a significant impact on renal scar formation, introducing a 2.51-fold risk (odds ratio 2.51, 95% confidence interval 1.04-6.04, P=0.04). The A1166C gene polymorphism was not significantly associated with the development of parenchymal damage in children with BD. Our findings introduce ACE I/D gene polymorphism as an independent risk factor for parenchymal destruction in pediatric patients with BD.