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The incidence of nephrolithiasis continues to rise. Previously, we showed that a monogenic cause could be detected in 11.4% of individuals with adult-onset nephrolithiasis or nephrocalcinosis and in 16.7-20.8% of individuals with onset before 18 years of age, using gene panel sequencing of 30 genes known to cause nephrolithiasis/nephrocalcinosis. To overcome the limitations of panel sequencing, we utilized whole exome sequencing in 51 families, who presented before age 25 years with at least one renal stone or with a renal ultrasound finding of nephrocalcinosis to identify the underlying molecular genetic cause of disease. In 15 of 51 families, we detected a monogenic causative mutation by whole exome sequencing. A mutation in seven recessive genes (AGXT, ATP6V1B1, CLDN16, CLDN19, GRHPR, SLC3A1, SLC12A1), in one dominant gene (SLC9A3R1), and in one gene (SLC34A1) with both recessive and dominant inheritance was detected. Seven of the 19 different mutations were not previously described as disease-causing. In one family, a causative mutation in one of 117 genes that may represent phenocopies of nephrolithiasis-causing genes was detected. In nine of 15 families, the genetic diagnosis may have specific implications for stone management and prevention. Several factors that correlated with the higher detection rate in our cohort were younger age at onset of nephrolithiasis/nephrocalcinosis, presence of multiple affected members in a family, and presence of consanguinity. Thus, we established whole exome sequencing as an efficient approach toward a molecular genetic diagnosis in individuals with nephrolithiasis/nephrocalcinosis who manifest before age 25 years., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Nephrolithiasis, a condition in which urinary supersaturation leads to stone formation in the urinary system, affects about 5%-10% of individuals worldwide at some point in their lifetime and results in significant medical costs and morbidity. To date, mutations in more than 30 genes have been described as being associated with nephrolithiasis, and these mutations explain about 15% of kidney stone cases, suggesting that additional nephrolithiasis-associated genes remain to be discovered. To identify additional genes whose mutations are linked to nephrolithiasis, we performed targeted next-generation sequencing of 18 hypothesized candidate genes in 348 unrelated individuals with kidney stones. We detected biallelic mutations in SLC26A1 (solute carrier family 26 member 1) in two unrelated individuals with calcium oxalate kidney stones. We show by immunofluorescence, immunoblotting, and glycosylation analysis that the variant protein mimicking p.Thr185Met has defects in protein folding or trafficking. In addition, by measuring anion exchange activity of SLC26A1, we demonstrate that all the identified mutations in SLC26A1 result in decreased transporter activity. Our data identify SLC26A1 mutations as causing a recessive Mendelian form of nephrolithiasis., (Copyright © 2016 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Background and Objectives: Nephrolithiasis is a prevalent condition that affects 10%-15% of adults in their lifetime. It is associated with high morbidity due to colicky pain, the necessity for surgical intervention, and sometimes progression to CKD. In recent years, multiple monogenic causes of nephrolithiasis and nephrocalcinosis have been identified. However, the prevalence of each monogenic gene in a pediatric renal stone cohort has not yet been extensively studied., Design, Setting, Participants, & Measurements: To determine the percentage of cases that can be explained molecularly by mutations in one of 30 known nephrolithiasis/nephrocalcinosis genes, we conducted a high-throughput exon sequencing analysis in an international cohort of 143 individuals <18 years of age, with nephrolithiasis (n=123) or isolated nephrocalcinosis (n=20). Over 7 months, all eligible individuals at three renal stone clinics in the United States and Europe were approached for study participation., Results: We detected likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 16.8% (24 of 143) of affected individuals; 12 of the 27 detected mutations were not previously described as disease causing (44.4%). We observed that in our cohort all individuals with infantile manifestation of nephrolithiasis or nephrocalcinosis had causative mutations in recessive rather than dominant monogenic genes. In individuals who manifested later in life, causative mutations in dominant genes were more frequent., Conclusions: We present the first exclusively pediatric cohort examined for monogenic causes of nephrolithiasis/nephrocalcinosis, and suggest that important therapeutic and preventative measures may result from mutational analysis in individuals with early manifestation of nephrolithiasis or nephrocalcinosis., (Copyright © 2016 by the American Society of Nephrology.)

Diagnosis and management of pediatric nephrolithiasis/nephrocalcinosis is a very complex and challenging task for every pediatrician. It is based on correct. disease history taking, which may guide to the mode of inheritance (dominant, recessive, x-linked). Ethnicity and consanguinity should also be investigated since they predispose to high prevalence of certain disorders. One should always begin with cheap and available screening tests. Herein we will review clinical, biochemical, metabolic and genetic characteristics of the inherited diseases which lead to nephrolithiasis/nephrocalcinosis, such as: idiopathic hypercalciuria, renal hypophosphatemia, renal tubular acidosis, idiopathic infantile hypercalcemia, Dent disease, familial hypomagnesemia with hypercalciuria and nephrocalcinosis, hypocitraturia, cystinuria, primary hyperoxaluria and renal hypouricemia. Modern genetic techniques such as next generation sequencing enable nowadays diagnosis of rare disease using only a blood sample, trough massive parallel resequencing of many genes. This is very helpful for anuric patients or on dialysis where blood and urine biochemistry are not informative. Genetic testing also replaces invasive liver biopsy or unpleasant acidification tests and enables prenatal or early postnatal diagnosis.

Nephrolithiasis is a prevalent condition with a high morbidity. Although dozens of monogenic causes have been identified, the fraction of single-gene disease has not been well studied. To determine the percentage of cases that can be molecularly explained by mutations in 1 of 30 known kidney stone genes, we conducted a high-throughput mutation analysis in a cohort of consecutively recruited patients from typical kidney stone clinics. The cohort comprised 272 genetically unresolved individuals (106 children and 166 adults) from 268 families with nephrolithiasis (n=256) or isolated nephrocalcinosis (n=16). We detected 50 likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 14.9% (40 of 268) of all cases; 20 of 50 detected mutations were novel (40%). The cystinuria gene SLC7A9 (n=19) was most frequently mutated. The percentage of monogenic cases was notably high in both the adult (11.4%) and pediatric cohorts (20.8%). Recessive causes were more frequent among children, whereas dominant disease occurred more abundantly in adults. Our study provides an in-depth analysis of monogenic causes of kidney stone disease. We suggest that knowledge of the molecular cause of nephrolithiasis and nephrocalcinosis may have practical implications and might facilitate personalized treatment., (Copyright © 2015 by the American Society of Nephrology.)

Vitamin D has several important functions including absorption of calcium and phosphorous, and facilitating normal immune system function. Sufficient amount of the vitamin is required for normal growth and development of bones and teeth, as well as improved resistance against certain diseases. There is growing evidence that there are huge benefits of vitamin D in promoting the human health, not only in infants for prevention of rickets but also effects on the immune system, blood pressure, reducing the risk of some cancers, prevention of diabetes mellitus type 1 trough stimulation of the pancreatic beta cells to secrete insulin. In contrast to these benefits certain patients genetically predisposed are at risk to develop a serious even fatal disease such as idiopathic infantile hypercalcemia. Withdrawal of vitamin D and reduction of calcium intake are lifesaving interventions for these babies. Recently it was found that recessive mutations in CYP24A1 gene are responsible for this disease. This gene encodes the enzyme 24 vitamin D hydroxylase which is important in the degradation metabolic pathway of the vitamin D. Although it was generally believed that idiopathic infantile hypercalcemia is the disease limited to infancy a number of studies yields that adults may have serious morbidity including nephrolithiasis, nephrocalcinosis, intermittent episodes of hypercalcemia leading to chronic kidney disease and in few cases to end stage renal disease. Therefore one should be very cautious in liberal prescribing vitamin D supplements and excessive exposure to sunlight, particularly in individuals with genetic predisposition. [ABSTRACT FROM AUTHOR]