Diagnosis and management of primary hyperoxalurias: best practices.

The primary hyperoxalurias (PH 1, 2, and 3) are rare autosomal recessive disorders of glyoxylate metabolism resulting in hepatic overproduction of oxalate. Clinical presentations that should prompt consideration of PH include kidney stones, nephrocalcinosis, and kidney failure of unknown etiology, especially with echogenic kidneys on ultrasound. PH1 is the most common and severe of the primary hyperoxalurias with a high incidence of kidney failure as early as infancy. Until the recent availability of a novel RNA interference (RNAi) agent, PH care was largely supportive of eventual need for kidney/liver transplantation in PH1 and PH2. Together with the Oxalosis and Hyperoxaluria Foundation, the authors developed a diagnostic algorithm for PH1 and in this report outline best clinical practices related to its early diagnosis, supportive treatment, and long-term management, including the use of the novel RNAi. PH1-focused approaches to dialysis and kidney/liver transplantation for PH patients with progression to chronic kidney disease/kidney failure and systemic oxalosis are suggested. Therapeutic advances for this devastating disease heighten the importance of early diagnosis and informed treatment.

Prospective Study of the Multisite Spread of a Medication Safety Intervention: Factors Common to Hospitals With Improved Outcomes.

Context and implementation approaches can impede the spread of patient safety interventions. The objective of this article is to characterize factors associated with improved outcomes among 9 hospitals implementing a medication safety intervention. Nephrotoxic Injury Negated by Just-in-Time Action (NINJA) is a pharmacist-driven intervention that led to a sustained reduction in nephrotoxic medication-associated acute kidney injury (NTMx-AKI) at 1 hospital. Using qualitative comparative analysis, the team prospectively assessed the association between context and implementation factors and NTMx-AKI reduction during NINJA spread to 9 hospitals. Five hospitals reduced NTMx-AKI. These 5 had either (1) a pharmacist champion and >2 pharmacists working on NINJA (Scon 1.0, Scov 0.8) or (2) a nephrologist-implementing NINJA with minimal competing organizational priorities (Scon 1.0, Scov 0.2). Interviews identified ways NINJA team leaders obtained pharmacist support or successfully implemented without that support. In conclusion, these findings have implications for future spread of NINJA and suggest an approach to study spread of safety interventions more broadly.

Treatment of primary hyperoxaluria type 1.

Supportive treatment for primary hyperoxaluria type 1 (PH1) focuses on high fluid intake and crystallization inhibitors. A subset of patients with specific PH1 genotypes (c.508G>A and c.454T>A) will respond to pyridoxine, defined as a >30% reduction in urinary oxalate excretion. Response to pyridoxine is variable and in some patients, urinary oxalate may normalize. The first focused treatment for PH1 using an RNA interference agent to reduce urinary oxalate was approved in 2020, and such therapies may significantly alter treatment approaches and long-term outcomes in PH1. Currently PH1 often presents with kidney function impairment and frequently results in end-stage kidney disease (ESKD). With kidney dysfunction, urinary oxalate clearance decreases and multisystem deposition of oxalate (oxalosis) occurs, commonly in bones, eyes, heart and skin. Once plasma oxalate levels exceed 30 µmol/L, aggressive haemodialysis is indicated to prevent oxalosis, even if the glomerular filtration rate (GFR) remains better than for typical dialysis initiation. Peritoneal dialysis alone does not achieve the needed oxalate clearance. Dialysis is a bridge to future transplantation. Liver transplantation restores hepatic alanine-glyoxylate transaminase enzyme activity, allowing glyoxylate detoxification and preventing further oxalosis. The native liver must be removed as part of this process to avoid ongoing pathologic oxalate production. The timing and type of liver transplantation are dependent on pyridoxine sensitivity, age, weight, residual GFR and evidence of systemic oxalate deposition in extrarenal organs. Liver transplant can be isolated or combined with kidney transplantation in a sequential or simultaneous fashion. Isolated kidney transplantation is generally reserved for pyridoxine-sensitive patients only. Although liver transplantation is curative for PH1 and kidney transplantation treats ESKD, ensuing necessary immunosuppression and potential allograft dysfunction impart significant long-term risks.

Treatment of post-transplant recurrent FSGS in children using plasmapheresis and augmentation of immunosuppression.

BACKGROUND: Up to 60% of pediatric renal transplant recipients with end-stage renal disease due to primary focal and segmental glomerulosclerosis (FSGS) may develop recurrent disease. Such recurrence is associated with poor prognosis if no remission is achieved. We report a single center experience with a protocol based on plasmapheresis and increased immunosuppression that resulted in a high long-lived remission rate. METHODS: This retrospective cohort study included consecutive pediatric renal transplant patients with recurrent FSGS treated with a standardized protocol using plasmapheresis and cyclophosphamide to supplement usual post-transplant immunosuppression with calcineurin inhibitors and steroids. Relapse was defined as urinary protein/creatinine ratio > 1.0 g/g and remission as < 0.5 g/g. RESULTS: Seventeen patients with FSGS recurrence post-transplant were treated. All had therapy resistant FSGS in native kidneys and had been on dialysis from 4 to 10 years. Of the 17, one died perioperatively from a pulmonary thromboembolism. Fifteen others achieved a complete remission within 3 months of treatment for FSGS recurrence. After a median follow-up period of 4 years, there were no recurrences of significant proteinuria. One patient achieved remission with rituximab. CONCLUSION: The addition of plasmapheresis and cyclophosphamide to a calcineurin- and steroid-based immunosuppression regime was highly successful in inducing high remission rates with recurrent FSGS. Prospective trials are needed to evaluate further the efficacy of increased immunosuppression along with plasmapheresis in this setting.

Reverse phenotyping facilitates disease allele calling in exome sequencing of patients with CAKUT.

PURPOSE: Congenital anomalies of the kidneys and urinary tract (CAKUT) constitute the leading cause of chronic kidney disease in children. In total, 174 monogenic causes of isolated or syndromic CAKUT are known. However, syndromic features may be overlooked when the initial clinical diagnosis of CAKUT is made. We hypothesized that the yield of a molecular genetic diagnosis by exome sequencing (ES) can be increased by applying reverse phenotyping, by re-examining the case for signs/symptoms of the suspected clinical syndrome that results from the genetic variant detected by ES. METHODS: We conducted ES in an international cohort of 731 unrelated families with CAKUT. We evaluated ES data for variants in 174 genes, in which variants are known to cause isolated or syndromic CAKUT. In cases in which ES suggested a previously unreported syndromic phenotype, we conducted reverse phenotyping. RESULTS: In 83 of 731 (11.4%) families, we detected a likely CAKUT-causing genetic variant consistent with an isolated or syndromic CAKUT phenotype. In 19 of these 83 families (22.9%), reverse phenotyping yielded syndromic clinical findings, thereby strengthening the genotype-phenotype correlation. CONCLUSION: We conclude that employing reverse phenotyping in the evaluation of syndromic CAKUT genes by ES provides an important tool to facilitate molecular genetic diagnostics in CAKUT.

Continued reduction in peritonitis rates in pediatric dialysis centers: results of the Standardizing Care to Improve Outcomes in Pediatric End Stage Renal Disease (SCOPE) Collaborative.

BACKGROUND: In its first 3 years, the Standardizing Care to Improve Outcomes in Pediatric End Stage Renal Disease (SCOPE) Collaborative demonstrated a statistically significant increase in the likelihood of compliance with a standardized follow-up care bundle and a significant reduction in peritonitis. We sought to determine if compliance with care bundles and low peritonitis rates could be sustained in centers continuously participating for 84 months. METHODS: Centers that participated from collaborative launch through the 84-month study period and provided pre-launch peritonitis rates were included. Children on maintenance peritoneal dialysis were eligible for enrollment. Changes in bundle compliance were assessed using a logistic regression model or a generalized linear mixed model (GLMM). Changes in average annualized peritonitis rates over time were modeled using GLMMs. RESULTS: Nineteen centers contributed 1055 patients with 1268 catheters and 17,247 follow-up encounters. The likelihood of follow-up compliance increased significantly over the study period (OR 1.05 95% confidence interval (CI) 1.03, 1.07; p < 0.001). Centers achieved ≥ 80% follow-up bundle compliance by 28 months and maintained a mean compliance of 84% between 28 and 84 months post-launch. Average monthly peritonitis rates decreased from 0.53 (95% CI 0.37, 0.70) infections per patient-year pre-launch to 0.30 (95% CI 0.23, 0.43) at 84 months post-launch, p < 0.001. CONCLUSIONS: Centers participating in the SCOPE Collaborative for 84 months achieved and maintained a high level of compliance with a standardized follow-up care bundle and demonstrated a significant and continued reduction in average monthly peritonitis rates.

Early outcomes comparing induction with antithymocyte globulin vs alemtuzumab in two steroid-avoidance protocols in pediatric renal transplantation.

Steroid avoidance in pediatric kidney transplants was found effective with extended daclizumab induction. Upon discontinuation of daclizumab, lymphocyte-depleting agents became used, with little comparative data. We assessed outcomes in children undergoing low immunologic-risk deceased donor (DD) kidney transplants using induction with antithymocyte globulin (ATG) compared to alemtuzumab. We reviewed consecutive DD kidney transplants from January 2015 to September 2017 at two pediatric centers that used different lymphocyte-depleting agents in steroid-avoidance protocols: ATG (Center A) and alemtuzumab (Center B), with tacrolimus and MMF as maintenance immunosuppression. Anti-infective prophylaxis was based on center protocol. Over the first year post-tx, there were similar rates of infections. EBV and BK viremia were comparable though Center A manifested more low-grade CMV viremia (A 46% vs B 0%; P = .0009) at median onset 1.8 months, followed by early seroconversion. Reduction of immunosuppression did not differ between groups. DSA at 1 year was similar (A 8% vs 13%) with low rates of BPAR. Need for steroid-based conversion was low. There were no graft losses and no differences in median eGFR at 30, 90, 180, and 365 days. (a) 1-year graft outcomes are excellent in steroid-avoidance regimens using ATG or alemtuzumab induction; (b) conversion to steroid-based therapy is low; (c) alemtuzumab/high-dose MMF is associated with lower WBC and more GCSF use; (d) alemtuzumab/higher dose MMF results in more diarrhea and azathioprine conversion than ATG/lower dose MMF; (e) CMV viremia is seen more often with ATG use with infection prophylaxis reduction; however, seroconversion occurs promptly.

A prospective multi-center quality improvement initiative (NINJA) indicates a reduction in nephrotoxic acute kidney injury in hospitalized children.

Nephrotoxic medication (NTMx) exposure is a common cause of acute kidney injury (AKI) in hospitalized children. The Nephrotoxic Injury Negated by Just-in time Action (NINJA) program decreased NTMx associated AKI (NTMx-AKI) by 62% at one center. To further test the program, we incorporated NINJA across nine centers with the goal of reducing NTMx exposure and, consequently, AKI rates across these centers. NINJA screens all non-critically ill hospitalized patients for high NTMx exposure (over three medications on the same day or an intravenous aminoglycoside over three consecutive days), and then recommends obtaining a daily serum creatinine level in exposed patients for the duration of, and two days after, exposure ending. Additionally, substitution of equally efficacious but less nephrotoxic medications for exposed patients starting the day of exposure was recommended when possible. The main outcome was AKI as defined by the Kidney Disease Improving Global Outcomes (KDIGO) serum creatinine criteria (increase of 50% or 0.3 mg/dl over baseline). The primary outcome measure was AKI episodes per 1000 patient-days. Improvement was defined by statistical process control methodology and confirmed by Autoregressive Integrated Moving Average (ARIMA) modeling. Eight consecutive bi-weekly measure rates in the same direction from the established baseline qualified as special cause change for special process control. We observed a significant and sustained 23.8% decrease in NTMx-AKI rates by statistical process control analysis and by ARIMA modeling; similar to those of the pilot single center. Thus, we have successfully applied the NINJA program to multiple pediatric institutions yielding decreased AKI rates.

Effects of changes in adult erythropoietin dosing guidelines on erythropoietin dosing practices, anemia, and blood transfusion in children on hemodialysis: findings from North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS).

BACKGROUND: While adult hemodialysis (HD) patients have increased morbidity with higher target hemoglobin levels, similar findings have not been demonstrated in pediatric patients. We evaluated changes in transfusions, anemia frequency, and erythropoietin (epo) dosing among pediatric HD patients before, during, and after implementation of federal dialysis payment policies regarding epo dosing for adult HD patients. METHODS: This is a retrospective cohort study of pediatric HD patients enrolled in NAPRTCS. We evaluated need for transfusion, anemia, median hemoglobin, and median epo dose 6 months after starting HD in 3 eras: baseline (2003-2007), implementation (2008-2011), and post implementation (2012-2016). We used multivariate logistic regression models to evaluate potential differences in transfusion across the eras. RESULTS: Six months after dialysis initiation, 12.6% of patients required transfusion pre-implementation, 17.9% during implementation, and 15.5% post implementation. Anemia occurred in 17.4% of patients pre, 23.5% during, and 23.8% post implementation, with median hemoglobin levels of 11.9 g/dL pre, 11 g/dL during, and 11 g/dL post implementation. Epo use was high across all 3 eras, but epo dosing decreased during and post implementation, despite more anemia during these periods. Odds of transfusion in implementation era compared with pre-implementation was 1.75 (95% CI 1.11-2.77) and odds of transfusion in post implementation era compared with pre was 1.19 (95% CI 0.71-1.98), controlling for age, race, gender, and prior transplant status. CONCLUSIONS: During and following implementation of adult epo dosing guidelines, transfusion and anemia frequency increased in pediatric HD patients. Ideal target hemoglobin levels for pediatric dialysis patients warrant further study.

Using Electronic Health Record Data to Rapidly Identify Children with Glomerular Disease for Clinical Research.

BACKGROUND: The rarity of pediatric glomerular disease makes it difficult to identify sufficient numbers of participants for clinical trials. This leaves limited data to guide improvements in care for these patients. METHODS: The authors developed and tested an electronic health record (EHR) algorithm to identify children with glomerular disease. We used EHR data from 231 patients with glomerular disorders at a single center to develop a computerized algorithm comprising diagnosis, kidney biopsy, and transplant procedure codes. The algorithm was tested using PEDSnet, a national network of eight children's hospitals with data on >6.5 million children. Patients with three or more nephrologist encounters (n=55,560) not meeting the computable phenotype definition of glomerular disease were defined as nonglomerular cases. A reviewer blinded to case status used a standardized form to review random samples of cases (n=800) and nonglomerular cases (n=798). RESULTS: The final algorithm consisted of two or more diagnosis codes from a qualifying list or one diagnosis code and a pretransplant biopsy. Performance characteristics among the population with three or more nephrology encounters were sensitivity, 96% (95% CI, 94% to 97%); specificity, 93% (95% CI, 91% to 94%); positive predictive value (PPV), 89% (95% CI, 86% to 91%); negative predictive value, 97% (95% CI, 96% to 98%); and area under the receiver operating characteristics curve, 94% (95% CI, 93% to 95%). Requiring that the sum of nephrotic syndrome diagnosis codes exceed that of glomerulonephritis codes identified children with nephrotic syndrome or biopsy-based minimal change nephropathy, FSGS, or membranous nephropathy, with 94% sensitivity and 92% PPV. The algorithm identified 6657 children with glomerular disease across PEDSnet, ≥50% of whom were seen within 18 months. CONCLUSIONS: The authors developed an EHR-based algorithm and demonstrated that it had excellent classification accuracy across PEDSnet. This tool may enable faster identification of cohorts of pediatric patients with glomerular disease for observational or prospective studies.

Evidence-based development of a nephrotoxic medication list to screen for acute kidney injury risk in hospitalized children.

PURPOSE: Medications are commonly associated with acute kidney injury (AKI). However, in both clinical practice and research, consideration of specific medications as nephrotoxic varies widely. The Nephrotoxic Injury Negated by Just-in-time Action quality improvement collaborative was formed to focus on prevention or reduction of nephrotoxic medication-associated AKI in noncritically ill hospitalized children. However, there were discrepancies among institutions as to which medications should be considered nephrotoxic. The collaborative convened a Nephrotoxic Medication (NTMx) Subcommittee to develop a consensus for the classification of nephrotoxic medications. SUMMARY: The NTMx Subcommittee initially included pediatric nephrologists, a pharmacist, and a pediatric intensivist. The committee reviewed NTMx lists from the collaborative and identified changes from the initial NTMx list. The NTMx Subcommittee conducted a literature review of the disputed medications and assigned an evidence grade based on the reported association with nephrotoxicity and the quality of the data. The association between medication exposure and AKI was also determined using administrative data from the Pediatric Health Information Systems database. The NTMx Subcommittee then came to a majority consensus regarding which medications should be included on the list. The subcommittee's recommendations were presented to the larger collaborative for approval, and consensus was achieved. The list continues to be reviewed and updated annually. CONCLUSION: Formation of a multicenter quality-improvement initiative exposed current limitations as to which medications are considered nephrotoxic in clinical and research settings and presented an opportunity to approach this problem using an evidence-based process. A consensus definition of nephrotoxic-medication exposure was achieved.

Renal replacement therapy in the management of intoxications in children: recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) workgroup.

BACKGROUND: Intentional or unintentional ingestions among children and adolescents are common. There are a number of ingestions amenable to renal replacement therapy (RRT). METHODS: We systematically searched PubMed/Medline, Embase, and Cochrane databases for literature regarding drugs/intoxicants and treatment with RRT in pediatric populations. Two experts from the PCRRT (Pediatric Continuous Renal Replacement Therapy) workgroup assessed titles, abstracts, and full-text articles for extraction of data. The data from the literature search was shared with the PCRRT workgroup and two expert toxicologists, and expert panel recommendations were developed. RESULTS AND CONCLUSIONS: We have presented the recommendations concerning the use of RRTs for treatment of intoxications with toxic alcohols, lithium, vancomycin, theophylline, barbiturates, metformin, carbamazepine, methotrexate, phenytoin, acetaminophen, salicylates, valproic acid, and aminoglycosides.

Whole-Exome Sequencing Enables a Precision Medicine Approach for Kidney Transplant Recipients.

BACKGROUND: Whole-exome sequencing (WES) finds a CKD-related mutation in approximately 20% of patients presenting with CKD before 25 years of age. Although provision of a molecular diagnosis could have important implications for clinical management, evidence is lacking on the diagnostic yield and clinical utility of WES for pediatric renal transplant recipients. METHODS: To determine the diagnostic yield of WES in pediatric kidney transplant recipients, we recruited 104 patients who had received a transplant at Boston Children's Hospital from 2007 through 2017, performed WES, and analyzed results for likely deleterious variants in approximately 400 genes known to cause CKD. RESULTS: By WES, we identified a genetic cause of CKD in 34 out of 104 (32.7%) transplant recipients. The likelihood of detecting a molecular genetic diagnosis was highest for patients with urinary stone disease (three out of three individuals), followed by renal cystic ciliopathies (seven out of nine individuals), steroid-resistant nephrotic syndrome (nine out of 21 individuals), congenital anomalies of the kidney and urinary tract (ten out of 55 individuals), and chronic glomerulonephritis (one out of seven individuals). WES also yielded a molecular diagnosis for four out of nine individuals with ESRD of unknown etiology. The WES-related molecular genetic diagnosis had implications for clinical care for five patients. CONCLUSIONS: Nearly one third of pediatric renal transplant recipients had a genetic cause of their kidney disease identified by WES. Knowledge of this genetic information can help guide management of both transplant patients and potential living related donors.

Infection-Related Glomerulonephritis.

Acute postinfectious glomerulonephritis or infection-related glomerulonephritis has been associated with several viral or bacterial infections. Group A beta-hemolytic streptococcal infection is the prototypical cause of postinfectious glomerulonephritis and the main focus of this discussion. The clinical spectrum can vary widely, from asymptomatic microscopic hematuria incidentally detected on routine urinalysis to rapidly progressive glomerulonephritis with acute kidney injury requiring emergent dialysis. Other important causes include glomerulonephritis associated with endocarditis and ventriculoatrial shunt infections. Multiple renal pathologic conditions have been associated with hepatitis B and C infections.

Whole-Exome Sequencing Identifies Causative Mutations in Families with Congenital Anomalies of the Kidney and Urinary Tract.

BACKGROUND: Congenital anomalies of the kidney and urinary tract (CAKUT) are the most prevalent cause of kidney disease in the first three decades of life. Previous gene panel studies showed monogenic causation in up to 12% of patients with CAKUT. METHODS: We applied whole-exome sequencing to analyze the genotypes of individuals from 232 families with CAKUT, evaluating for mutations in single genes known to cause human CAKUT and genes known to cause CAKUT in mice. In consanguineous or multiplex families, we additionally performed a search for novel monogenic causes of CAKUT. RESULTS: In 29 families (13%), we detected a causative mutation in a known gene for isolated or syndromic CAKUT that sufficiently explained the patient's CAKUT phenotype. In three families (1%), we detected a mutation in a gene reported to cause a phenocopy of CAKUT. In 15 of 155 families with isolated CAKUT, we detected deleterious mutations in syndromic CAKUT genes. Our additional search for novel monogenic causes of CAKUT in consanguineous and multiplex families revealed a potential single, novel monogenic CAKUT gene in 19 of 232 families (8%). CONCLUSIONS: We identified monogenic mutations in a known human CAKUT gene or CAKUT phenocopy gene as the cause of disease in 14% of the CAKUT families in this study. Whole-exome sequencing provides an etiologic diagnosis in a high fraction of patients with CAKUT and will provide a new basis for the mechanistic understanding of CAKUT.

Exit site and tunnel infections in children on chronic peritoneal dialysis: findings from the Standardizing Care to Improve Outcomes in Pediatric End Stage Renal Disease (SCOPE) Collaborative.

BACKGROUND: The Standardizing Care to Improve Outcomes in Pediatric End Stage Renal Disease (SCOPE) Collaborative is a quality improvement initiative to reduce dialysis-associated infections. The frequency of peritoneal dialysis (PD) catheter exit site infection (ESI) and variables influencing its development and end result are unclear. We sought to determine ESI rates, to elucidate the epidemiology, risk factors, and outcomes for ESI, and to assess for association between provider compliance with care bundles and ESI risk. METHODS: We reviewed demographic, dialysis and ESI data, and care bundle adherence and outcomes for SCOPE enrollees from October 2011 to September 2014. ESI involved only the exit site, only the subcutaneous catheter tunnel, or both. RESULTS: A total of 857 catheter insertions occurred in 734 children over 10,110 cumulative months of PD provided to these children. During this period 207 ESIs arose in 124 children or 0.25 ESIs per dialysis year. Median time to ESI was 392 days, with 69% of ESIs involving exit site only, 23% involving the tunnel only, and 8% involving both sites. Peritonitis developed in 6%. ESI incidence was associated with age (p = 0.003), being the lowest in children aged < 2 years and highest in those aged 6-12 years, and with no documented review of site care or an exit site score of > 0 at prior month's visit (p < 0.001). Gender, race, end stage renal disease etiology, exit site orientation, catheter cuff number or mobilization, and presence of G-tube, stoma, or vesicostomy were unassociated with ESI incidence. Of the ESIs reported, 71% resolved with treatment, 24% required hospitalization, and 9% required catheter removal, generally secondary to tunnel infection. CONCLUSIONS: Exit site infections occur at an annualized rate of 0.25, typically well into the dialysis course. Younger patient age and documented review of site care are associated with lower ESI rates. Although most ESIs resolve, hospitalization is frequent, and tunnel involvement/catheter loss complicate outcomes.

Whole Exome Sequencing Reveals a Monogenic Cause of Disease in ≈43% of 35 Families With Midaortic Syndrome.

Midaortic syndrome (MAS) is a rare cause of severe childhood hypertension characterized by narrowing of the abdominal aorta in children and is associated with extensive vascular disease. It may occur as part of a genetic syndrome, such as neurofibromatosis, or as consequence of a pathological inflammatory disease. However, most cases are considered idiopathic. We hypothesized that in a high percentage of these patients, a monogenic cause of disease may be detected by evaluating whole exome sequencing data for mutations in 1 of 38 candidate genes previously described to cause vasculopathy. We studied a cohort of 36 individuals from 35 different families with MAS by exome sequencing. In 15 of 35 families (42.9%), we detected likely causal dominant mutations. In 15 of 35 (42.9%) families with MAS, whole exome sequencing revealed a mutation in one of the genes previously associated with vascular disease (NF1, JAG1, ELN, GATA6, and RNF213). Ten of the 15 mutations have not previously been reported. This is the first report of ELN, RNF213, or GATA6 mutations in individuals with MAS. Mutations were detected in NF1 (6/15 families), JAG1 (4/15 families), ELN (3/15 families), and one family each for GATA6 and RNF213 Eight individuals had syndromic disease and 7 individuals had isolated MAS. Whole exome sequencing can provide conclusive molecular genetic diagnosis in a high fraction of individuals with syndromic or isolated MAS. Establishing an etiologic diagnosis may reveal genotype/phenotype correlations for MAS in the future and should, therefore, be performed routinely in MAS.