Making Decisions About Krabbe Disease Newborn Screening

Current Status of Newborn Bloodspot Screening Worldwide 2024: A Comprehensive Review of Recent Activities (2020-2023)

Newborn bloodspot screening (NBS) began in the early 1960s based on the work of Dr. Robert "Bob" Guthrie in Buffalo, NY, USA. His development of a screening test for phenylketonuria on blood absorbed onto a special filter paper and transported to a remote testing laboratory began it all. Expansion of NBS to large numbers of asymptomatic congenital conditions flourishes in many settings while it has not yet been realized in others. The need for NBS as an efficient and effective public health prevention strategy that contributes to lowered morbidity and mortality wherever it is sustained is well known in the medical field but not necessarily by political policy makers. Acknowledging the value of national NBS reports published in 2007, the authors collaborated to create a worldwide NBS update in 2015. In a continuing attempt to review the progress of NBS globally, and to move towards a more harmonized and equitable screening system, we have updated our 2015 report with information available at the beginning of 2024. Reports on sub-Saharan Africa and the Caribbean, missing in 2015, have been included. Tables popular in the previous report have been updated with an eye towards harmonized comparisons. To emphasize areas needing attention globally, we have used regional tables containing similar listings of conditions screened, numbers of screening laboratories, and time at which specimen collection is recommended. Discussions are limited to bloodspot screening.

Newborn Screening for Neurodevelopmental Disorders May Exacerbate Health Disparities

Newborn screening (NBS) began in the early 1960s with screening for phenylketonuria on blood collected on filter paper. The number of conditions included in NBS programs expanded significantly with the adoption of tandem mass spectrometry. The recommended uniform screening panel provides national guidance and has reduced state variability. Universality and uniformity have been supported to promote equity. Recently, a number of researchers have suggested expanding NBS to include genomic sequencing to identify all genetic disorders in newborns. This has been specifically suggested for genes that increase the risk for neurodevelopmental disorders (NDDs), with the presumption that early identification in the newborn period would reduce disabilities. We offer arguments to show that genomic sequencing of newborns for NDDs risks exacerbating disparities. First, the diagnosis of NDD requires clinical expertise, and both genetic and neurodevelopmental expertise are in short supply, leading to disparities in access to timely follow-up. Second, therapies for children with NDDs are insufficient to meet their needs. Increasing early identification for those at risk who may never manifest developmental delays could shift limited resources to those children whose parents are more poised to advocate, worsening disparities in access to services. Rather, we suggest an alternative: genomic sequencing of all children with diagnosed NDDs. This focused strategy would have the potential to target genomic sequencing at children who manifest NDDs across diverse populations which could better improve our understanding of contributory genes to NDDs.

CD8+ T cell depletion prevents neuropathology in a mouse model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD) or Krabbe's disease is a fatal genetic demyelinating disease of the central nervous system caused by loss-of-function mutations in the galactosylceramidase (galc) gene. While the metabolic basis for disease is known, the understanding of how this results in neuropathology is not well understood. Herein, we report that the rapid and protracted elevation of CD8+ cytotoxic T lymphocytes occurs coincident with clinical disease in a mouse model of GLD. Administration of a function-blocking antibody against CD8α effectively prevented disease onset, reduced morbidity and mortality, and prevented CNS demyelination in mice. These data indicate that subsequent to the genetic cause of disease, neuropathology is driven by pathogenic CD8+ T cells, thus offering novel therapeutic potential for treatment of GLD.

Gene Therapy of Sphingolipid Metabolic Disorders

Sphingolipidoses are defined as a group of rare hereditary diseases resulting from mutations in the genes encoding lysosomal enzymes. This group of lysosomal storage diseases includes more than 10 genetic disorders, including GM1-gangliosidosis, Tay-Sachs disease, Sandhoff disease, the AB variant of GM2-gangliosidosis, Fabry disease, Gaucher disease, metachromatic leukodystrophy, Krabbe disease, Niemann-Pick disease, Farber disease, etc. Enzyme deficiency results in accumulation of sphingolipids in various cell types, and the nervous system is also usually affected. There are currently no known effective methods for the treatment of sphingolipidoses; however, gene therapy seems to be a promising therapeutic variant for this group of diseases. In this review, we discuss gene therapy approaches for sphingolipidoses that are currently being investigated in clinical trials, among which adeno-associated viral vector-based approaches and transplantation of hematopoietic stem cells genetically modified with lentiviral vectors seem to be the most effective.

A neglected neurodegenerative disease: Adult-onset globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD), or Krabbe disease (KD) is a rare neurodegenerative disease, and adult-onset GLD is more even neglected by clinicians. This review provides detailed discussions of the serum enzymes, genes, clinical manifestations, neuroimaging features, and therapies of GLD, with particular emphasis on the characteristics of adult-onset GLD, in an attempt to provide clinicians with in-depth insights into this disease.

Why must the debate continue on Krabbe disease newborn screening?

Since the early 2000s, many families impacted by Krabbe disease have tried to implement newborn screening for this rare fatal neurological disorder in their home state. However, despite grassroots efforts, states have been unable to agree to newborn screening for Krabbe disease due to poor testing mechanisms, lack of understanding of the developmental outcomes of transplantation, low incidence rate, and more. Over the past five years, many organizations and experts have made significant strides to help Krabbe disease meet the eligibility requirements for state panels and the Recommended Uniform Screening Panel (RUSP). Nevertheless, ethicists and newborn screening advisory committees continue to disregard the progress our community has made in the treatment and screening of Krabbe disease.