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.

Case report: Two siblings with very late onset of holocarboxylase synthase deficiency and a mini-review.

Holocarboxylase synthase (HCS) deficiency is an extremely rare metabolic disorder typically presenting as severe neonatal metabolic acidosis, lethargy, hypotonia, vomiting, and seizures. This report describes two siblings in a family with late-onset forms of HCS deficiency. The younger sister presented at the age of 11 years and manifested as acute metabolic acidosis, which promptly resolved following rehydration and biotin administration. The results of the organic urine profile confirmed multiple carboxylase deficiency, and genetic testing revealed a novel pathogenic variant in the HLCS gene (NM_000411.8) in the homozygous state: c.995A>G; p. (Gln332Arg). No further decompensation was observed for her during the 3-year follow-up period. His older brother was diagnosed at the age of 23 years-old through biochemical tests, without any history of acidotic decompensation. A mini-review of HCS deficiency with late onset (>1 year) or early onset (<1 month) revealed that splice variants are associated with late onset, while both variants p. (Leu216Arg) and p. (Leu237Pro) are associated with early onset. However, the majority of genotypes do not show a clear correlation with the timing of HCS deficiency onset. The most significant point here is the description of extremely late-onset cases of HCS deficiency. This can prompt metabolic investigations and raise suspicion of this rare disease in cases of unexplained metabolic acidosis, even beyond early childhood.

Case report: Unveiling genetic and phenotypic variability in Nonketotic hyperglycinemia: an atypical early onset case associated with a novel GLRX5 variant.

Nonketotic hyperglycinemia (NKH) is a rare, autosomal recessive metabolic disorder usually associated with mutations in genes AMT, GLDC or GCSH involved in the glycine cleavage complex. Other genes have been linked with less severe NKH, associated with deficiency of lipoate cofactor such as GLRX5, LIAS, BOLA3. We identified a new case of GLRX5-mediated NKH who presented at 2-month with severe developmental delay and seizures. The initial suspicion was raised by the MRI and then confirmed by glycine measurements in cerebrospinal fluid and blood. Genetic analysis revealed a previously undescribed homozygous variant in the GLRX5 gene [NM_016417.3:c.367G>C; p. (Asp123His)]. Despite medication and supportive care, he died at the age of 4 months after a sudden neurological deterioration. It was decided to limit therapeutic interventions due to the severity of the prognosis. The case was more severe than the previous GLRX5-mediated NKH described, regarding the early age at onset and the severity. Moreover, the genetic variant was located at a potentially crucial site for glutathione binding in the GLRX5 protein. This report, thereby, expands our understanding of NKH's genetic underpinnings and phenotypic variability, highlighting the crucial role of GLRX5 and other related genes in variant NKH.

Nutritional impact of CFTR modulators in children with cystic fibrosis.

Background: Nutritional status is a major prognostic factor for breathing and the survival of patients with cystic fibrosis (CF). Since 2012, the development of CFTR modulators has considerably transformed the outcome of this disease. Indeed, both lung function and body mass index are improved by CFTR modulators, such as Lumacaftor/Ivacaftor. However, few data exist regarding the outcome of nutritional intakes under Lumacaftor/Ivacaftor. Methods: We conducted a prospective single-center study in children with CF treated with Lumacaftor/Ivacaftor to evaluate their nutritional intake before and after treatment. Results: Thirty-four children were included in this study, with a median age of 12.4 years [11.9; 14.7]. There was no significant improvement in weight, height or BMI. Patients' total energy intake was not significantly changed with Lumacaftor/Ivacaftor, while carbohydrate intakes decreased significantly. We found that blood levels of vitamin E and Selenium were significantly increased under Lumacaftor/Ivacaftor, without a significant increase in supplementation. In patients with a BMI Z-score < 0 at treatment initiation, there was a significant improvement in weight and BMI Z-score, while TEI and carbohydrate intakes were significantly lower. Conclusion: We showed that treatment with Lumacaftor/Ivacaftor improved the nutritional status of patients without necessarily being associated with an increase in nutritional intake. Although these data need to be confirmed in larger cohorts, they support the hypothesis that weight gain under modulators is multifactorial, and may be related to a decrease in energy expenditure or an improvement in absorption.

Dietary intake assessment in children with cystic fibrosis using 3-day food diaries: a single-centre study.

Background: Malnutrition is both a feature and major cause of morbidity in cystic fibrosis (CF). Therefore, nutritional management is an essential element of patient care. In 2016, an international guideline for nutritional management in patients with CF was published. In light of these recommendations, the aim of this study was to investigate the dietary intake of children with CF at the University Hospital of Bordeaux. Methods: We conducted a retrospective study at the Paediatric CF Centre of the University Hospital of Bordeaux. Patients aged 2-18 years with CF who completed a 3-day food diary at home between January 2015 and December 2020 were included. Results: A total of 130 patients, with a median age of 11.8 [interquartile range (IQR): 8.3; 13.4] years, were included. The median Z-score for BMI was -0.35 (IQR: -0.9; 0.2) and 20% of the patients had a Z-score for BMI < -1. Recommended total energy intakes were achieved in 53% of the patients, particularly those with nutritional support. Recommended protein intake was met in 28% of the cases, while fat and carbohydrate intakes were met in 54%. Vitamin and micronutrient levels were normal in 80% of the patients, with the exception of vitamin K, which was within the therapeutic range in only 42% of the cases. Conclusion: Recommended nutritional targets are difficult to achieve in patients with CF, and providing nutritional support during follow-up remains a challenge.