Assessment of epidemiology and outcomes of adult patients with kidney-limited thrombotic microangiopathies.

Thrombotic microangiopathies (TMA) are usually associated with hematological features (RH-TMA). The epidemiology of TMA limited to kidneys (RL-TMA) is unclear Therefore, patients with TMA and native kidney biopsies were identified during 2009-2022 in 20 French hospitals and results evaluated. RL-TMA was present in 341/757 (45%) patients and associated with lower creatinine levels (median 184 vs 346 µmol/L) than RH-TMA. RL-TMA resulted from virtually all identified causes, more frequently from anti-VEGF treatment and hematological malignancies but less frequently from shigatoxin-associated hemolytic uremic syndrome (HUS), systemic sclerosis, gemcitabine and bacterial infection, and even less frequently when three or more causes/triggers were combined (RL-TMA: 5%; RH-TMA: 12%). RL-TMA was associated with significantly lower major cardiovascular events (10% vs 20%), kidney replacement therapy (23% vs 43%) and death (12% vs 20%) than RH-TMA during follow-up (median 28 months). Atypical HUS (aHUS) was found in 326 patients (RL-TMA: 43%, RH-TMA: 44%). Among the 69 patients with proven complement-mediated aHUS, eculizumab (anti-C5 therapy) was used in 43 (62%) (RL-TMA: 35%; RH-TMA: 71%). Among the 257 other patients with aHUS, including 51% with RL-TMA, eculizumab was used in 29 but with unclear effects of this treatment. Thus, RL-TMA represents a very high proportion of patients with TMA and results from virtually all known causes of TMA and includes 25% of patients with complement-mediated aHUS. Adverse outcomes of RL-TMA are lower compared to RH-TMA but remain significant. Anti-C5 therapy was rarely used in RL-TMA, even in proven complement-mediated aHUS, and its effects remain to be assessed.

Reassuring pregnancy outcomes in women with mild COL4A3-5-related disease (Alport syndrome) and genetic type of disease can aid personalized counseling.

Individualized pre-pregnancy counseling and antenatal care for women with chronic kidney disease (CKD) require disease-specific data. Here, we investigated pregnancy outcomes and long-term kidney function in women with COL4A3-5 related disease (Alport Syndrome, (AS)) in a large multicenter cohort. The ALPART-network (mAternaL and fetal PregnAncy outcomes of women with AlpoRT syndrome), an international collaboration of 17 centers, retrospectively investigated COL4A3-5 related disease pregnancies after the 20th week. Outcomes were stratified per inheritance pattern (X-Linked AS (XLAS)), Autosomal Dominant AS (ADAS), or Autosomal Recessive AS (ARAS)). The influence of pregnancy on estimated glomerular filtration rate (eGFR)-slope was assessed in 192 pregnancies encompassing 116 women (121 with XLAS, 47 with ADAS, and 12 with ARAS). Median eGFR pre-pregnancy was over 90ml/min/1.73m2. Neonatal outcomes were favorable: 100% live births, median gestational age 39.0 weeks and mean birth weight 3135 grams. Gestational hypertension occurred during 23% of pregnancies (reference: 'general' CKD G1-G2 pregnancies incidence is 4-20%) and preeclampsia in 20%. The mean eGFR declined after pregnancy but remained within normal range (over 90ml/min/1.73m2). Pregnancy did not significantly affect eGFR-slope (pre-pregnancy ß=-1.030, post-pregnancy ß=-1.349). ARAS-pregnancies demonstrated less favorable outcomes (early preterm birth incidence 3/11 (27%)). ARAS was a significant independent predictor for lower birth weight and shorter duration of pregnancy, next to the classic predictors (pre-pregnancy kidney function, proteinuria, and chronic hypertension) though missing proteinuria values and the small ARAS-sample hindered analysis. This is the largest study to date on AS and pregnancy with reassuring results for mild AS, though inheritance patterns could be considered in counseling next to classic risk factors. Thus, our findings support personalized reproductive care and highlight the importance of investigating kidney disease-specific pregnancy outcomes.

Fertility Management in Cystinosis: A Clinical Perspective.

Cystinosis is a rare, inherited, lysosomal storage disorder characterized by the progressive accumulation of intralysosomal cystine and subsequent organ and tissue damage. The kidneys are the first and most severely impacted organ. Although cystinosis was once considered a fatal pediatric disease, patients with cystinosis are living well into adulthood with advances in medical care, including kidney transplant and early and continuous use of cysteamine therapy. This increase in life expectancy has revealed an extrarenal phenotype of cystinosis that emerges in adolescence and adulthood, affecting nearly all body systems, including the endocrine and reproductive systems. As individuals with cystinosis are planning for the future, reproductive health and fertility have become areas of increased focus. This narrative review aims to summarize the current understanding of reproductive health and fertility in patients with cystinosis and discuss practical considerations for monitoring and managing these complications.

Pubertal origin of growth retardation in inborn errors of protein metabolism: A longitudinal cohort study.

OBJECTIVES: Inherited amino-acid metabolism disorders (IAAMDs) require lifelong protein-restricted diet. We aimed to investigate: 1/ whether IAAMDs was associated with growth, pubertal, bone mineral apparent density (BMAD) or body composition impairments; 2/ associations linking height, amino-acid mixture (AAM), plasma amino-acids and IGF1 concentrations. DESIGN: Retrospective longitudinal study of 213 patients with neonatal-onset urea cycle disorders (UCD,n = 77), organic aciduria (OA,n = 89), maple syrup urine disease (MSUD,n = 34), or tyrosinaemia type 1 (n = 13). METHODS: We collected growth parameters, pubertal status, BMAD, body composition, protein-intake, and IGF1 throughout growth. RESULTS: Overall final height (n = 69) was below target height (TH): -0.9(1.4) vs. -0.1(0.9) SD, p < 0.001. Final height was ≤ TH-2SD in 12 (21%) patients. Height ≤ - 2SD was more frequent during puberty than during early-infancy and pre-puberty: 23.5% vs. 6.9%, p = 0.002; and vs. 10.7%, p < 0.001. Pubertal delay was frequent (26.7%). Height (SD) was positively associated with isoleucine concentration: ß, 0.008; 95%CI, 0.003 to 0.012; p = 0.001. In the pubertal subgroup, height (SD) was lower in patients with vs. without AAM supplementation: -1.22 (1.40) vs. -0.63 (1.46) (p = 0.02). In OA, height and median (IQR) isoleucine and valine concentrations(µmol/L) during puberty were lower in patients with vs. without AAM supplementation: -1.75 (1.30) vs. -0.33 (1.55) SD, p < 0.001; and 40 (23) vs. 60 (25) (p = 0.02) and 138 (92) vs. 191 (63) (p = 0.01), respectively. No correlation was found with IGF1. Lean-mass index was lower than fat-mass index: -2.03 (1.15) vs. -0.44 (0.89), p < 0.001. CONCLUSIONS: In IAAMDs, growth retardation worsened during puberty which was delayed in all disease subgroups. Height seems linked to the disease, AAM composition and lower isoleucine concentration, independently of the GH-IGF1 pathway. We recommend close monitoring of diet during puberty.

Worldwide disparities in access to treatment and investigations for nephropathic cystinosis: a 2023 perspective.

BACKGROUND: Nephropathic cystinosis (NC) is a rare lysosomal disease, leading to early kidney failure and extra-renal comorbidities. Its prognosis strongly relies on early diagnosis and treatment by cysteamine. Developing economies (DEing) face many challenges when treating patients for rare and chronic diseases. The aim here is to evaluate the access to investigations and treatment in DEing, and to assess for potential inequalities with Developed Economies (DEed). METHODS: In this international cross-sectional study, a questionnaire on access, price and reimbursement of genetic, biological analyses, and treatment was sent to nephrology centers worldwide during 2022. RESULTS: A total of 109 centers responded, coming from 49 countries and managing 741 patients: 43 centers from 30 DEing and Economies in transition (TrE), and 66 from 19 DEed. In 2022, genetics availability was 63% in DEing and 100% in DEed, whereas intra leukocytes cystine levels (IL-CL) were available for 30% of DEing patients, and 94% of DEed patients, both increasing over the last decade, as has access to immediate release cysteamine and to cysteamine eye drops in DEing. However, delayed released cysteamine can be delivered to only 7% vs. 74% of patients from DEing and DEed, respectively, and is still poorly reimbursed in DEing. CONCLUSIONS: Over the last decade, access to investigations (namely genetics and IL-CL) and to cysteamine have improved in DEing and TrE. However, discrepancies remain with DEed: access to delayed released cysteamine is limited, and reimbursement is still profoundly insufficient, therefore limiting their current use.

Systemic primary carnitine deficiency induces severe arrhythmia due to shortening of QT interval.

BACKGROUND: Systemic primary carnitine deficiency (PCD) is characterized by cardiomyopathy and arrhythmia. Without carnitine supplementation, progression is usually towards fatal cardiac decompensation. While the cardiomyopathy is most likely secondary to energy deficiency, the mechanism of arrhythmia is unclear, and may be related to a short QT interval. OBJECTIVE: We aim to describe rhythmic manifestations at diagnosis and with carnitine supplementation. METHODS: French patients diagnosed for PCD were retrospectively included. Clinical and para clinical data at diagnosis and during follow-up were collected. Electrocardiograms with QT interval measurements were blinded reviewed by two paediatric cardiologists. RESULTS: Nineteen patients (median age at diagnosis 2.3 years (extremes 0.3-28.9)) followed in 8 French centres were included. At diagnosis, 21% of patients (4/19) had arrhythmia (2 ventricular fibrillations, 1 ventricular tachycardia and 1 sudden death), and 84% (16/19) had cardiomyopathy. Six electrocardiograms before treatment out of 11 available displayed a short QT (QTc < 340 ms). Median corrected QTc after carnitine supplementation was 404 ms (extremes 341-447) versus 350 ms (extremes 282-421) before treatment (p < 0.001). The whole QTc was prolonged, and no patient reached the criterion of short QT syndrome with carnitine supplementation. Three patients died, probably from rhythmic cause without carnitine supplementation (two extra-hospital sudden deaths and one non-recoverable rhythmic storm before carnitine supplementation), whereas no rhythmic complication occurred in patients with carnitine supplementation. CONCLUSION: PCD is associated with shortening of the QT interval inducing severe arrhythmia. A potential explanation would be a toxic effect of accumulated fatty acid and metabolites on ionic channels embedded in the cell membrane. Carnitine supplementation normalizes the QTc and prevents arrhythmia. Newborn screening of primary carnitine deficiency would prevent avoidable deaths.

Rare Variants in Complement Gene in C3 Glomerulopathy and Immunoglobulin-Mediated Membranoproliferative GN.

BACKGROUND: C3 glomerulopathy and idiopathic immunoglobulin-mediated membranoproliferative GN (Ig-MPGN) are rare complement-mediated kidney diseases. Inherited forms of C3 glomerulopathy/Ig-MPGN are rarely described. METHODS: Three hundred ninety-eight patients with C3 glomerulopathy ( n =296) or Ig-MPGN ( n =102) from a national registry were screened for three complement genes: factor H ( CFH ), factor I ( CFI ), and C3 . Patients with rare variant (minor allele frequency <0.1%) were included. Epidemiologic, clinical, and immunologic data at diagnosis and kidney outcomes of patients were retrospectively collected. RESULTS: Fifty-three different rare variants, including 30 (57%), 13 (24%), and ten (19%) in CFH , CFI , and C3 variants, were identified in 66/398 (17%) patients. Thirty-eight (72%) variants were classified as pathogenic, including 20/30 (66%) and 11/13 (84%) variants in CFH and CFI , respectively, impairing synthesis of factor H or factor I regulators. Fifteen of 53 (27%) variants were of unknown significance. At diagnosis, 69% of patients were adult (median age of 31 years). With the exception of biologic stigma of thrombotic microangiopathy, which was more frequent in patients with CFI variants (5/14 [36%] versus 1/37 [3%] and 0% in the CFH group and C3 group, respectively, P < 0.001), the clinical and histologic features were similar among the three variants groups. The kidney outcome was poor regardless of the age at onset and treatment received. Sixty-five percent (43/66) of patients with rare variant reach kidney failure after a median delay of 41 (19-104) months, compared with 28% (55/195) after a median delay of 34 (12-143) months in the nonvariant group. Among 36 patients who received a kidney transplant, 2-year recurrence was frequent, occurring in 39% (12/31), without difference between variant groups, and led to graft failure in three cases. CONCLUSIONS: In our cohort, 17% of C3 glomerulopathy/Ig-MPGN cases were associated with rare variants in the CFH , CFI , or C3 genes. In most cases, a quantitative deficiency in factor H or factor I was identified. The presence of a rare variant was associated with poor kidney survival. PODCAST: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/CJASN/2023_11_08_CJN0000000000000252.mp3.

The genetic landscape and clinical spectrum of nephronophthisis and related ciliopathies.

Nephronophthisis (NPH) is an autosomal-recessive ciliopathy representing one of the most frequent causes of kidney failure in childhood characterized by a broad clinical and genetic heterogeneity. Applied to one of the worldwide largest cohorts of patients with NPH, genetic analysis encompassing targeted and whole exome sequencing identified disease-causing variants in 600 patients from 496 families with a detection rate of 71%. Of 788 pathogenic variants, 40 known ciliopathy genes were identified. However, the majority of patients (53%) bore biallelic pathogenic variants in NPHP1. NPH-causing gene alterations affected all ciliary modules defined by structural and/or functional subdomains. Seventy six percent of these patients had progressed to kidney failure, of which 18% had an infantile form (under five years) and harbored variants affecting the Inversin compartment or intraflagellar transport complex A. Forty eight percent of patients showed a juvenile (5-15 years) and 34% a late-onset disease (over 15 years), the latter mostly carrying variants belonging to the Transition Zone module. Furthermore, while more than 85% of patients with an infantile form presented with extra-kidney manifestations, it only concerned half of juvenile and late onset cases. Eye involvement represented a predominant feature, followed by cerebellar hypoplasia and other brain abnormalities, liver and skeletal defects. The phenotypic variability was in a large part associated with mutation types, genes and corresponding ciliary modules with hypomorphic variants in ciliary genes playing a role in early steps of ciliogenesis associated with juvenile-to-late onset NPH forms. Thus, our data confirm a considerable proportion of late-onset NPH suggesting an underdiagnosis in adult chronic kidney disease.

Complement-driven hemolytic uremic syndrome.

Overactivation of the complement alternative pathway drives the pathogenesis of primary atypical hemolytic uremic syndrome (aHUS). Genetically-determined or acquired dysregulation of the complement is frequently identified in patients with aHUS, pregnancy-related hemolytic uremic syndrome (HUS), and severe hypertension-associated HUS. In contrast, it is still unclear whether self-limited complement activation, which frequently occurs in other forms of HUS, provides key mechanistic clues or results from endothelial damage. Development of novel biomarkers is underway to firmly establish complement-driven pathogenesis. C5 blockade therapy has revolutionized the management of aHUS patients, resulting in a halving of the subpopulation under chronic dialysis over the course of a few years. On the other hand, the efficacy of C5 blockade in secondary forms of HUS, as assessed by small and uncontrolled case series, is less compelling and should be investigated through properly designed prospective clinical trials. The increased risk of meningococcal infection, related to C5 inhibition, must be rigorously addressed with suitable prophylaxis. Treatment duration should be determined based on an individualized benefit/risk assessment.

Outcome of infantile nephropathic cystinosis depends on early intervention, not genotype: A multicenter sibling cohort study.

Infantile nephropathic cystinosis (INC) is an inheritable lysosomal storage disorder characterized by lysosomal cystine accumulation, progressive kidney disease, and multiple extrarenal complications (ERCs). Cysteamine postpones the onset of end-stage kidney disease (ESKD) and reduces the incidence of ERCs; however, cysteamine is generally initiated upon establishment of the renal Fanconi syndrome (FS) and partial loss of kidney function, whereas data on long-term effects of cysteamine administered from neonatal age are lacking. An international multicenter retrospective cohort study of siblings with INC was set up to investigate the outcome in relation to age at initiation of cysteamine versus CTNS genotype, with attention to patients treated with cysteamine from neonatal age. None of the siblings treated from neonatal age (n = 9; age 10 ± 6 years) had reached ESKD, while 22% of their index counterparts (n = 9; age 14 ± 5 years) had commenced renal replacement therapy. Siblings treated with cysteamine from the onset of symptoms at a younger age compared with their index counterparts, reached ESKD at a significant older age (13 ± 3 vs. 10 ± 3 years, p = 0.002). In contrast, no significant difference in ERCs was observed between sibling and index patients, independently from the age at initiation of cysteamine. The CTNS genotype had no impact on the overall outcome in this cohort. In INC, presymptomatic treatment with cysteamine results in a better renal outcome in comparison to treatment initiated from the onset of symptoms. This justifies including cystinosis into newborn screening programs. SYNOPSIS: In infantile nephropathic cystinosis, presymptomatic treatment with cysteamine improves the renal outcome which justifies the inclusion of cystinosis into newborn screening programs.

Idiopathic nephrotic syndrome relapse following COVID-19 vaccination: a series of 25 cases.

Background: Several cases of idiopathic nephrotic syndrome (INS) relapse following the administration of coronavirus disease 2019 (COVID-19) vaccines have recently been reported, raising questions about the potential relationship between the immune response to COVID-19 vaccination and INS pathogenesis. Methods: We performed a retrospective multicentre survey describing the clinical and biological characteristics of patients presenting a relapse of INS after COVID-19 vaccination, with an assessment of outcome under treatment. Results: We identified 25 patients (16 men and 9 women) presenting a relapse within 1 month of a COVID-19 vaccine injection. The glomerular disease was of childhood onset in half of the patients and most patients (21/25) had received at least one immunosuppressive drug in addition to steroids for frequently relapsing or steroid-dependent nephrotic syndrome (NS). All patients were in a stable condition at the time of injection and 11 had no specific treatment. In five patients, the last relapse was reported >5 years before vaccine injection. The Pfizer-BioNTech (BNT162b2) vaccine was used in 80% of the patients. In 18 cases, INS relapse occurred after the first injection, a mean of 17.5 days after vaccination. A second injection was nevertheless administered in 14 of these patients. Five relapses occurred after administration of the second dose and two relapses after the administration of the third dose. All but one of the patients received steroids as first-line treatment, with an additional immunosuppressive agent in nine cases. During follow-up, complete remission was achieved in 21 patients, within 1 month in 17 cases. Only one patient had not achieved at least partial remission after 3 months of follow-up. Conclusions: This case series suggests that, in rare patients, COVID-19 vaccination may trigger INS relapse that is generally easy to control. These findings should encourage physicians to persuade their patients to complete the COVID-19 vaccination schedule.

Expert guidance on the multidisciplinary management of cystinosis in adolescent and adult patients.

Cystinosis, a rare autosomal recessive lysosomal storage disorder, results in an abnormal accumulation of the amino acid cystine in multiple organs and tissues of the body. Renal symptoms typically develop in the first few months of life, with extra-renal manifestations becoming apparent over the next 10-20 years, which require coordinated multidisciplinary care. Here, we describe a consensus-based guidance to support the management of adolescents and adults living with cystinosis. The programme was led by a Steering Committee (SC) of six experts in the management of patients with cystinosis, who identified a list of 15 key questions reflecting the multi-organ effects of cystinosis. An Extended Faculty (EF) of eight additional specialists was invited to answer the questions via an online digital platform using a quasi-Delphi approach. The consolidated answers were summarized into recommendations. Where evidence was lacking, recommendations were developed using collective expert consensus. The EF was asked to agree/disagree with the clinical recommendations. The expert-agreed clinical recommendations provide guidance that considers both renal and extra-renal systems. The topics covered are advice on fertility and family planning, consideration of the nervous, muscular, ophthalmic, cardio-respiratory, endocrine, dermatological and gastrointestinal systems, as well as guidance on dental care, diet, lifestyle, and improving quality of life and psychological well-being. In summary, this work outlines recommendations and a checklist for clinicians with a vision for improving and standardizing the multidisciplinary care for patients with cystinosis.

Pregnancy in cystinosis patients with chronic kidney disease: A European case series.

Cystinosis is a rare autosomal recessive disease leading to end-stage renal disease within the second or third decade of life. Since the era of specific treatment with cysteamine, prognosis has substantially improved and pregnancy becomes an increasing concern. Pregnancy data in patients with cystinosis were collected through an anonymized survey. We collected data for 19 pregnancies in 12 women. Seventeen patients were transplanted, 1 was on hemodialysis and 1 had chronic kidney disease (CKD) stage 4. These 19 pregnancies resulted in 13 live births (68.4%): 3 spontaneous early miscarriages, 1 ectopic pregnancy, 1 early pre-eclampsia (at 21 weeks), and 1 preterm birth with neonatal death at 24 weeks were reported. After exclusion of early miscarriage or termination, pregnancy success rate was 86.7%. In successful pregnancies, median gestational age at delivery was 34 weeks (24-37). Preeclampsia occurred in seven pregnancies (7/15, 46.7%). A cesarean section was performed in all pregnancies. Median baby weight at delivery was 2175 g (620-3374 g). After pregnancy, one patient reached end-stage renal disease, but she already had advanced CKD before pregnancy (creatinine 239 µmol/L, eGFR 23 ml/min/1.73 m2 ). In three other patients, there was a decrease of eGFR of 8, 20, and 53 ml/min/1.73 m2 , respectively. The majority of pregnancies were successful, but severe antenatal and post-natal complications may occur, in particular preeclampsia that was noticed in nearly half of patients and fetal loss in one-third of them. These results may help pre-pregnancy counseling and pregnancy management.

Results from a nationwide retrospective cohort measure the impact of C3 and soluble C5b-9 levels on kidney outcomes in C3 glomerulopathy.

C3 glomerulopathy (C3G) is a rare complement-mediated disease. Specific treatments are not yet available and factors predictive of kidney survival such as age, kidney function and proteinuria are not specific to C3G. The prognostic value of biomarkers of complement activation, which are pathognomonic of the diseases, remains unknown. In a large cohort of 165 patients from the French National registry, we retrospectively assess the prognostic value of C3, soluble C5b-9 (sC5b-9), C3 nephritic factor, and rare disease-predicting variants in complement genes in predicting clinical outcome of patients. By multivariate analysis age (adult onset), reduced kidney function (defined by estimated glomerular filtration rate under 60ml/min) and presence of rare disease-predicting variants in complement genes predicted risk of progression to kidney failure. Moreover, by multivariate analysis, normal C3/high sC5b-9 levels or low C3/normal sC5b-9 levels remained independently associated with a worse kidney prognosis, with the relative risk 3.7- and 8-times higher, respectively. Subgroup analysis indicated that the complement biomarker profiles independently correlated to kidney prognosis in patients with adult but not pediatric onset. In this subgroup, we showed that profiles of biomarkers C3 and/or sC5b-9 correlated with intra glomerular inflammation and may explain kidney outcomes. In children, only the presence of rare disease-predicting variants correlated with kidney survival. Thus, in an adult population, we propose a three-point C3G prognostic score based on biomarker profiles at risk, estimated glomerular filtration rate at presentation and genetic findings, which may help stratify adult patients into subgroups that require close monitoring and more aggressive therapy.

Very long-term outcomes in 23 patients with cblA type methylmalonic acidemia.

OBJECTIVES: To present the very long-term follow up of patients with cobalamin A (cblA) deficiency. METHODS: A retrospective case series of adult (>16 years) patients with molecular or enzymatic diagnosis of cblA deficiency. RESULTS: We included 23 patients (mean age: 27 ± 7.6 years; mean follow-up: 24.9 ± 7.6 years). Disease onset was mostly pediatric (78% < 1 year, median = 4 months) with acute neurologic deterioration (65%). Eight patients presented with chronic symptoms, and one had an adult-onset mild cblA deficiency. Most of the patients (61%) were initially classified as vitamin B12-unresponsive methylmalonic aciduria (MMA); in vitro B12 responsiveness was subsequently found in all the tested patients (n = 13). Initial management consisted of protein restriction (57%), B12 (17%), or both (26%). The main long-term problems were intellectual disability (39%) and renal failure (30%). However, 56.5% of the patients were living independently. Intellectual disability was equally distributed among the initial treatment groups, while renal failure (moderate and beginning at the age of 38 years) was present in only one out of seven patients initially treated with B12. CONCLUSIONS: We provide a detailed picture of the long-term outcome of a series of adult cblA patients, mostly diagnosed before the enzymatic and molecular era. We confirm that about 35% of the patients do not present acutely, underlining the importance of measuring MMA in any case of unexplained chronic renal failure, intellectual disability, or growth delay. In addition, we describe a patient with a milder adult-onset form. Early B12 supplementation seems to protect from severe renal insufficiency.

Intravenous administration of a branched-chain amino-acid-free solution in children and adults with acute decompensation of maple syrup urine disease: a prospective multicentre observational study.

BACKGROUND: Patients with maple syrup urine disease (MSUD) experiencing metabolic decompensations have traditionally been treated with branched-chain amino acid (BCAA)-free mixture via oral or nasogastric administration routes. In some patients, enteral administration is not possible, either because the patient presents with vomiting, coma, or refuses nasogastric administration, thus intravenous (IV) BCAA-free solution is an appropriate intervention for these challenging cases. AIMS: This study aimed to evaluate the effectiveness and safety of managing metabolic decompensations by administering an IV BCAA-free solution. METHODS: This is an observational prospective study of data from MSUD patients hospitalised for decompensation episodes between 2010 and 2016 at 6 centres for rare metabolic diseases in France. RESULTS: A total of 24 patients (16 males; 8 females) experiencing 126 MSUD metabolic decompensation episodes (39 in children; 87 in adults) were admitted to hospital. At presentation, mean leucine plasma concentration was ≥ 381 µmol/L in 113/126 (89.7%) episodes. Children were treated with continuous IV BCAA-free solution at doses of 0.8 to 2.0 g/kg/day, for 4.8 days and adults for 3.8 days at doses of 0.5 to 2.6 g/kg/day. In the efficacy set of 102 analysable episodes leucine concentrations were normalised (to below 381 µmol/L) in 82% (n = 18/22) of episodes in children and in 84% (n = 67/80) of episodes in adults. Mean time to leucine normalisation was 3.0 days. This was significantly (p < 0.001) shorter than the algorithmically predicted time to leucine normalisation with traditional BCAA-free mixture. Duration of hospitalisation was significantly longer for children than for adults (7.1 days in children vs 5.2 days in adults, p = 0.012). No treatment-related adverse events were reported in any patients on IV BCAA-free solution. CONCLUSION: The IV BCAA-free solution is safe and effective in normalising leucine concentrations during MSUD decompensation episodes in both children and adults, offering a practical treatment alternative for those patients who cannot receive BCAA-free mixture via oral or nasogastric routes.