Severe neuromuscular forms of glycogen storage disease type IV: Histological, clinical, biochemical, and molecular findings in a large French case series

Glycogen storage disease type IV (GSD IV), also called Andersen disease, or amylopectinosis, is a highly heterogeneous autosomal recessive disorder caused by a glycogen branching enzyme (GBE, 1,4-alpha-glucan branching enzyme) deficiency secondary to pathogenic variants on GBE1 gene. The incidence is evaluated to 1:600 000 to 1:800 000 of live births. GBE deficiency leads to an excessive deposition of structurally abnormal, amylopectin-like glycogen in affected tissues (liver, skeletal muscle, heart, nervous system, etc.). Diagnosis is often guided by histological findings and confirmed by GBE activity deficiency and molecular studies. Severe neuromuscular forms of GSD IV are very rare and of disastrous prognosis. Identification and characterization of these forms are important for genetic counseling for further pregnancies. Here we describe clinical, histological, enzymatic, and molecular findings of 10 cases from 8 families, the largest case series reported so far, of severe neuromuscular forms of GSD IV along with a literature review. Main antenatal features are: fetal akinesia deformation sequence or arthrogryposis/joint contractures often associated with muscle atrophy, decreased fetal movement, cystic hygroma, and/or hydrops fetalis. If pregnancy is carried to term, the main clinical features observed at birth are severe hypotonia and/or muscle atrophy, with the need for mechanical ventilation, cardiomyopathy, retrognathism, and arthrogryposis. All our patients were stillborn or died within 1 month of life. In addition, we identified five novel GBE1 variants.

Pleural penetration of amoxicillin and metronidazole during pleural infection: An ambispective cohort study

OBJECTIVES

The pharmacokinetics of antibiotics in pleural fluid during pleural infections has been poorly described. This study aimed to explore amoxicillin and metronidazole diffusion into the pleural space.

METHODS

This was an ambispective, single-centre study that included patients with complicated parapneumonic effusion or pleural empyema managed with repeated therapeutic thoracentesis as first-line treatment between 2014 and 2022. Pleural steady-state or trough concentrations of amoxicillin and metronidazole were measured, with a lower limit of quantification of 5 mg/L.

RESULTS

Seventy paired blood and pleural samples were analysed from 40 patients. The median (interquartile range) patient age was 55 years (45-67 years) and 88% were male. The median patient weight was 65.8 kg (57.3-82 kg) and median plasma albumin concentration was 29.7 g/L (23.7-33.9 g/L). Median creatinine clearance was 106 mL/min (95-117 mL/min). Median amoxicillin pleural concentrations in patients treated with oral, bolus and continuous intravenous administrations (6 g/day) were, respectively, 5.2 (<5-6.4), 9.4 (8-13.1) and 10.8 (7.1-13.1) mg/L. Pleural concentrations were <5 mg/L in 5/11 samples (45%) with oral treatment and 6/59 (10%) with intravenous treatment. Median metronidazole pleural concentrations were 18.4 (15.7-22.8) mg/L, with all patients being treated orally (1.5 g/day).

CONCLUSIONS

Oral metronidazole (1.5 g/day) and intravenous amoxicillin (6 g/day) achieved therapeutic targets in pleural fluid in most cases, but oral amoxicillin did not.

Avoiding falsely low creatinine concentrations measured in patients treated with N-acetylcysteine for acetaminophen intoxication using enzymo-amperometric method - An in vitro and in vivo study

BACKGROUND

Circulating creatinine is a biomarker of paramount importance in clinical practice. In cases of acetaminophen (APAP) intoxication, the antidote, N-acetylcysteine (NAC), interferes with commonly used creatininase-peroxidase methods. This study aimed to assess whether creatininase-amperometric methods were affected in this context.

METHODS

This study includes in vitro interference tests, involving four creatinine assays using NAC-spiked plasma pools and an in vivo retrospective study comparing creatininase-peroxidase and creatininase-amperometric measurements in patients presenting with NAC-treated APAP poisoning.

RESULTS

Creatininase-peroxidase method was impacted by NAC interference in a clinically-significant manner at therapeutic NAC levels (basal value recovery of 80 % and 70 % for 500 and 1000 mg.L-1 of NAC, respectively), surpassing the desirable Reference Change Value (RCV%). Enzymo-amperometric methods were not impacted. Among patients, a mean bias of -45.2 ± 28.0 % was observed for the peroxidase detection method compared to the amperometric in those who received NAC prior plasma sampling and -2.7 ± 5.4 % in those who did not.

CONCLUSIONS

Our findings indicate that enzymo-amperometric creatinine assays remain unaffected by NAC interference due to the absence of the peroxidase step in the analytical process. Therefore, these methods are suitable to prevent spurious hypocreatininemia in APAP intoxicated patients undergoing NAC therapy.

Early detection of plasma d-lactate: Toward a new highly-specific biomarker of bacteraemia?

Background

Bloodstream infections are a leading cause of mortality. Their detection relies on blood cultures (BCs) but time to positivity is often between tens of hours and days. d-lactate is a metabolite widely produced by bacteria but very few in human. We aimed to evaluate d-lactate, d-lactate/l-lactate ratio and d-lactate/total lactate ratio in plasma as potential early biomarkers of bacteraemia on a strictly biological standpoint.

Methods

A total of 228 plasma specimens were collected from patients who had confirmed bacteraemia (n = 131) and healthy outpatients (n = 97). Specific l-lactate and d-lactate analyses were performed using enzymatic assays and analytical performances of d-lactate, d-lactate/total lactate and d-lactate/l-lactate ratios for the diagnosis of bacteraemia were assessed.

Results

A preliminary in vitro study confirmed that all strains of Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus were able to produce d-lactate at significant levels. In patients, plasma d-lactate level was the most specific biomarker predicting a bacteraemia profile with a specificity and predictive positive value of 100% using a cut-off of 131 μmol.L^-1. However, sensitivity and negative predictive value were rather low, estimated at 31% and 52%, respectively. d-lactate displayed an Area Under Receiver Operating Characteristic (AUROC) curve of 0.696 with a P value < 0.0001. There was no difference of d-lactate levels between BCs bottles positive for Gram-positive or Gram-negative bacteria (p = 0.55).

Conclusion

d-lactate shows promise as a specific early biomarker of bacterial metabolism. The development of rapid automated assays could raise clinical applications for infectious diseases diagnosis including early bacteraemia prediction.

Newborn Screening of Primary Carnitine Deficiency: An Overview of Worldwide Practices and Pitfalls to Define an Algorithm before Expansion of Newborn Screening in France

Primary Carnitine Deficiency (PCD) is a fatty acid oxidation disorder that will be included in the expansion of the French newborn screening (NBS) program at the beginning of 2023. This disease is of high complexity to screen, due to its pathophysiology and wide clinical spectrum. To date, few countries screen newborns for PCD and struggle with high false positive rates. Some have even removed PCD from their screening programs. To understand the risks and pitfalls of implementing PCD to the newborn screening program, we reviewed and analyzed the literature to identify hurdles and benefits from the experiences of countries already screening this inborn error of metabolism. In this study, we therefore, present the main pitfalls encountered and a worldwide overview of current practices in PCD newborn screening. In addition, we address the optimized screening algorithm that has been determined in France for the implementation of this new condition.

Clinical relevance and antimicrobial susceptibility profile of the unknown human pathogen Corynebacterium aurimucosum

Introduction. Even though Corynebacterium aurimucosum has been described in 2002, this species has long been underestimated due to the unreliability of conventional identification methods and only a few cases of infections have been reported.Hypothesis/Gap Statement. Little is known about clinical significance and antimicrobial susceptibility profile of this uncommon species.Aim. To evaluate the clinical relevance of C. aurimucosum and its antimicrobial susceptibility profile.Methodology. All C. aurimucosum isolates, collected from 2010 to 2019 in 10 French university hospitals, were retrospectively included. Demographic, clinical and microbiological data were collected for all cases. Antimicrobial susceptibility testing was performed according to the 2019 EUCAST guidelines.Results. Fifty-seven clinical isolates of C. aurimucosum were collected in 57 patients (median age, 65.8 years; male/female sex ratio, 1.1), mostly from urine (28 %), blood culture (28 %) and bone/synovial fluid (19 %) samples. Of them, 14 cases of infection were confirmed, mainly bone and joint infections (50 %) followed by urinary tract infections (UTIs) (21 %), bacteremia (14 %), skin and soft-tissue infections (14 %). C. aurimucosum was recovered in pure culture in 36 % of cases (UTIs and bacteremia) while mixed cultures were observed for other infections. By testing 52 clinical isolates in vitro, this species appeared to be fully susceptible to linezolid and vancomycin while most isolates (>80 %) were susceptible to amoxicillin (MIC₉₀, 2 µg ml^-1), gentamicin, tetracycline and rifampicin. Both cefotaxime and ciprofloxacin seemed to have a limited activity (ca. 50 % of susceptible strains). The MIC distribution for ciprofloxacin showed a bimodal profile with a population of highly-resistant strains with MICs >2 µg ml^-1. Most isolates (>90 %) were categorized as resistant to penicillin G and clindamycin.Conclusion. C. aurimucosum should be considered as an actual opportunistic pathogen, and treatment with amoxicillin, vancomycin or linezolid should be preferred.