Preventing hyperhomocysteinemia using vitamin B6 supplementation in Givosiran-treated acute intermittent porphyria: Highlights from a case report and brief literature review.

Acute hepatic porphyrias are inherited metabolic disorders of heme biosynthesis characterized by the accumulation of toxic intermediate metabolites responsible for disabling acute neurovisceral attacks. Givosiran is a newly approved siRNA-based treatment of acute hepatic porphyria targeting the first and rate-limiting δ-aminolevulinic acid synthase 1 (ALAS1) enzyme of heme biosynthetic pathway. We described a 72-year old patient who presented with severe inaugural neurological form of acute intermittent porphyria evolving for several years which made her eligible for givosiran administration. On initiation of treatment, the patient developed a major hyperhomocysteinemia (>400 µmol/L) which necessitated to discontinue the siRNA-based therapy. A thorough metabolic analysis in the patient suggests that hyperhomocysteinemia could be attributed to a functional deficiency of cystathionine ß-synthase (CBS) enzyme induced by givosiran. Long-term treatment with vitamin B6, a cofactor of CBS, allowed to normalize homocysteinemia while givosiran treatment was maintained. We review the recently published cases of hyperhomocysteinemia in acute hepatic porphyria and its exacerbation under givosiran therapy. We also discuss the benefits of vitamin B6 supplementation in the light of hypothetic pathophysiological mechanisms responsible for hyperhomocysteinemia in these patients. Our results confirmed the importance of monitoring homocysteine metabolism and vitamin status in patients with acute intermittent porphyria in order to improve management by appropriate vitamin supplementation during givosiran treatment.

Hyperhomocysteinemia in acute hepatic porphyria (AHP) and implications for treatment with givosiran.

INTRODUCTION: Homocysteine is a sulfur-containing amino acid formed in the intermediary metabolism of methionine. Amino acid metabolism and heme biosynthesis pathways are complexly intertwined. Plasma homocysteine elevation, hyperhomocysteinemia (HHcy), has been reported in patients with acute hepatic porphyria (AHP), a family of rare genetic disorders caused by defects in hepatic heme biosynthesis. AREAS COVERED: This article summarizes published case series in which givosiran, a subcutaneously administered small interfering RNA approved for AHP treatment, appeared to exacerbate dysregulated homocysteine metabolism in patients with AHP. A comprehensive exploratory analysis of ENVISION trial data demonstrated that on a population level, givosiran increased homocysteine but with wide interpatient variations, and there is no proof of correlations between HHcy and changes in efficacy or safety of givosiran. EXPERT OPINION: The strong correlation and co-increase of homocysteine and methionine suggest that HHcy associated with givosiran is likely attributable to the impaired trans-sulfuration pathway catalyzed by cystathionine ß-synthase, which uses vitamin B6 as a cofactor. Data-based consensus supports monitoring total plasma homocysteine and vitamin B6, B12, and folate levels before and during givosiran treatment; supplementing with pyridoxine/vitamin B6 in patients with homocysteine levels >100 µmol/L; and involving patients with homocysteine levels >30 µmol/L in decisions to supplement.

Clinical Prediction of Iron Deficiency at Age 2 Years: A National Cross-sectional Study in France.

OBJECTIVE: To assess the diagnostic accuracy of existing clinical criteria and to develop prediction tools for iron deficiency in 2-year-old children. STUDY DESIGN: In a national cross-sectional study conducted in primary care pediatricians' practices throughout France, 2-year-old children were consecutively included (2016-2017). Multivariable logistic regression modeling and bootstrapping were used to develop several clinical models to predict iron deficiency (serum ferritin <12 µg/L). These models used the best criteria and combinations among the American Academy of Pediatrics' (AAP) criteria adapted to the European context (n = 10), then all potential predictors (n = 19). One model was then simplified into a simple prediction tool. RESULTS: Among 568 included infants, 38 had iron deficiency (6.7%). In univariable analyses, no significant association with iron deficiency was observed for 8 of the 10 adapted AAP criteria. Three criteria (both parents born outside the European Union, low weight at 1 year old, and weaning to cow's milk without supplemental iron) were retained in the AAP model, which area under the receiver operating characteristic curve, sensitivity, and specificity were 0.62 (95% CI, 0.58-0.67), 30% (95% CI, 22%-39%), and 95% (95% CI, 92%-97%), respectively. Four criteria were retained in a newly derived simple prediction tool (≥1 criterion among the 3 previous plus duration of iron-rich formula consumption <12 months), which area under the receiver operating characteristic curve, sensitivity, and specificity were 0.72 (95% CI, 0.65-0.79), 63% (95% CI, 47%-80%), and 81% (95% CI, 70%-91%), respectively. CONCLUSIONS: All prediction tools achieved acceptable diagnostic accuracy. The newly derived simple prediction tool offered potential ease of use. TRIAL REGISTRATION: ClinicalTrials.gov NCT02484274.

Young children formula consumption and iron deficiency at 24 months in the general population: A national-level study.

BACKGROUND & AIMS: Iron deficiency (ID) is considered the most frequent micronutrient deficiency in industrialized countries where strategies for its primary prevention vary widely and are insufficiently evaluated. We aimed to study the effectiveness for iron status of a national iron deficiency prevention strategy based on recommendations for young-child formula (YCF) use after age 12 months, taking into consideration other sources of iron and the family's socio-economic status. METHODS: In a cross-sectional observational study conducted in primary care pediatrician offices throughout France from 2016 to 2017, infants aged 24 months were consecutively included for a food survey and blood sampling. Associations between YCF consumption and serum ferritin (SF) level were studied by multivariable regression after adjustment on sociodemographic, perinatal and dietary characteristics, notably other intakes of iron. RESULTS: Among the 561 infants analyzed, the ID prevalence was 6.6% (37/561; 95% confidence interval [CI] 4.7-9.0). Daily iron intake excluding YCF and total daily iron intake including YCF were below the 5-mg/day recommended average requirements for 63% and 18% of children, respectively. ID frequency was significantly decreased (or SF level was independently higher) with any YCF consumption after age 10 months (odds ratio 0.15, 95% CI 0.07-0.31), current YCF consumption at age 24 months (median SF level 29 vs 21 µg/L if none), prolonged YCF consumption (28 µg/L if >12 months vs 17 µg/L if none), and increasing daily volume of YCF consumed at age 24 months from a small volume (e.g., 29 µg/L if <100 mL/day vs 21 µg/L if none). CONCLUSIONS: Current or past YCF use was independently associated with a better iron status at age 24 months than non-use. The strategy recommending YCF use at weaning after age 12 months seems effective in the general population. CLINICALTRIALS. GOV IDENTIFIER: NCT02484274.

Very low prevalence of iron deficiency among young French children: A national cross-sectional hospital-based survey.

Although iron deficiency (ID) is considered the most frequent micronutrient deficiency in industrialized countries and is associated with impaired neurodevelopment when occurring in early years, accurate recent estimations of its prevalence are lacking. Our objective was to estimate ID prevalence and associated sociodemographic markers in young children in France. The Saturn-Inf national cross-sectional hospital-based survey recruited 3,831 French children <6 years old between 2008 and 2009 to assess lead poisoning prevalence and to establish a biobank. This secondary analysis measured serum ferritinemia (SF) in sera kept frozen at -80 °C for children with sufficient serum aliquots and C-reactive protein <10 mg/L. For the 657 participating children (17% of the Saturn-Inf study), the median age was 3.9 years (interquartile range: 2.2-5.1); 52% were boys. The median SF was 44 µg/L (interquartile range: 28-71). ID prevalence was 2.8% (95% confidence interval [1.7, 4.7]) and 3.2% (95% confidence interval [2.0, 5.1]) with an SF threshold of 10 and 12 µg/L, respectively. Low SF was significantly associated (p < .05) with mother being a migrant (32 vs. 45 µg/L for a mother born in France) or unemployed (37 vs. 50 µg/L for a mother employed). In this first national cross-sectional hospital-based study in France, ID prevalence was much lower than that in other French and European studies performed in underprivileged populations but close to the lowest values observed in other population-based studies in Europe.