Newborn Screening For Metachromatic Leukodystrophy In Northern Germany- A Prospective Study

Metachromatic leukodystrophy (MLD) is a rare, fatal autosomal-recessive genetic disorder caused by insufficient activity of the enzyme arylsulfatase A (ARSA) that results in intra-lysosomal accumulation of the ARSA substrate galactosylceramide I3-sulfate (sulfatide), inevitably leading to progressive demyelination and neurodegeneration in the CNS and PNS. There are three variants of MLD commonly described in the literature based on the age at which symptoms appear: late-infantile MLD, juvenile MLD, and adult MLD. Children affected by MLD display progressive neurologic symptoms, including ataxia, seizures, and quadriplegia, culminating in severe disability and early death. MLD diagnosis is often delayed or missed. We have initiated a prospective newborn screening study with implementation of MLD into the current newborn screening panel for all newborns in the German states. The total birth rate in this area is approximately 55,000 live births per year. A tiered screening approach is being applied where sulfatide levels are measured in dried blood spots, followed by genetic confirmatory testing (ARSA, SUMF1, and PSAP genes). A technical validation including intra-run, inter-run, linearity, LLOQ have been performed. Clearly elevated levels of C16:0 and C16:1:OH were found for all five positive controls. Data have shown that age group dependent cut-offs is critical when using the assay also for confirmation testing and diagnostic purposes in infants, juveniles and adults. The sulfatide concentrations within the NBS group was significantly lower. We have measured over 15,000 samples up to date. Planned study duration is an initial 12 months with extension for another one to two years.