27 research outputs found
Guidelines for diagnosis and management of the cobalamin-related remethylation disorders cblC, cblD, cblE, cblF, cblG, cblJ and MTHFR deficiency
BACKGROUND: Remethylation defects are rare inherited disorders in which impaired remethylation of homocysteine to methionine leads to accumulation of homocysteine and perturbation of numerous methylation reactions.
OBJECTIVE: To summarise clinical and biochemical characteristics of these severe disorders and to provide guidelines on diagnosis and management.
DATA SOURCES: Review, evaluation and discussion of the medical literature (Medline, Cochrane databases) by a panel of experts on these rare diseases following the GRADE approach.
KEY RECOMMENDATIONS: We strongly recommend measuring plasma total homocysteine in any patient presenting with the combination of neurological and/or visual and/or haematological symptoms, subacute spinal cord degeneration, atypical haemolytic uraemic syndrome or unexplained vascular thrombosis. We strongly recommend to initiate treatment with parenteral hydroxocobalamin without delay in any suspected remethylation disorder; it significantly improves survival and incidence of severe complications. We strongly recommend betaine treatment in individuals with MTHFR deficiency; it improves the outcome and prevents disease when given early
The Newborn Screening Paradox : Sensitivity vs. Overdiagnosis in VLCAD Deficiency
OBJECTIVE: To improve the efficacy of newborn screening (NBS) for very long chain acyl-CoA dehydrogenase deficiency (VLCADD). PATIENTS AND METHODS: Data on all dried blood spots collected by the Dutch NBS from October 2007 to 2010 (742.728) were included. Based solely on the C14:1 levels (cutoff â„0.8 ÎŒmol/L), six newborns with VLCADD had been identified through NBS during this period. The ratio of C14:1 over C2 was calculated. DNA of all blood spots with a C14:1/C2 ratio of â„0.020 was isolated and sequenced. Children homozygous or compound heterozygous for mutations in the ACADVL gene were traced back and invited for detailed clinical, biochemical, and genetic evaluation. RESULTS: Retrospective analysis based on the C14:1/C2 ratio with a cutoff of â„0.020 identified an additional five children with known ACADVL mutations and low enzymatic activity. All were still asymptomatic at the time of diagnosis (age 2-5 years). Increasing the cutoff to â„0.023 resulted in a sensitivity of 93% and a positive predictive value of 37%. The sensitivity of the previously used screening approach (C14:1 â„0.8) was 50%. CONCLUSION: This study shows that the ratio C14:1/C2 is a more sensitive marker than C14:1 for identifying VLCADD patients in NBS. However, as these patients were all asymptomatic at the time of diagnosis, this suggests that a more sensitive screening approach may also identify individuals who may never develop clinical disease. Long-term follow-up studies are needed to establish the risk of these VLCADD-deficient individuals for developing clinical signs and symptoms