A team led by University of Washington biochemist Dr. Michael Gelb (pictured here) and including the MLD Foundation's Teryn and Dean Suhr, launched a pilot study for MLD newborn screening in the state of Washington based on findings first published in the journal Clinical Chemistry.
The incidence of metachromatic leukodystrophy, or MLD is not well understood. It is estimated to affect 1 in 40,000 to 1 in 160,000 births, but historically it has been poorly diagnosed because its symptoms mirror more common diseases, such as cerebral palsy.
The development of this newborn screening speaks to the recent achievements in the treatment of MLD. Newborn screening is only considered for a condition when there is a treatment, and until recently, MLD had no meaningful therapeutic options. That changed when the results from a gene therapy trial in 2013 led by Boston Children's Hospital's Dr. Alessandra Biffi were published in the journal Science. Dr Gelb explains: "The treatment works so well that interest in newborn screening [for MLD] is escalating."
Currently, MLD is diagnosed biochemically by analyzing urine samples for the elevated presence of sulfatides. But with nearly 4 million infants born in the US each year, collecting urine samples was infeasible. The challenge for Dr. Gelb and his team was developing a technique to extract sulfatides using dried blood from the heel prick tests already administered to newborns.
Using a mass spectrometer,* Gelb and his colleagues detected meaningful concentrations of the substance and were able to stratify sulfatide levels and associate them with disease severity. The most common form of MLD, late-infantile onset MLD, affecting 60 percent of known cases, strikes children between the ages of 12 and 24 months; 1 out of 3 patients get diagnosed with juvenile onset MLD that presents in children between the ages of 3 and the teen years, and the rarest form of the disease occurs in adults. The earlier the onset of symptoms, the more fast-progressing the disease is.
The pilot study will last around three years and include “maybe 80,000 or 100,000 samples,” Gelb explained, to get a sense of the false-positive rate across the population
“If we got 50 hits, that would be fine; we’d follow those patients. But if we got a thousand hits, based on what we think about the prevalence of the disease, the pilot would fail because it would not be feasible to follow that many children.”
This is not the first time Dr. Gelb has pioneered a newborn screening for a leukodystrophy and other related lysosmal storage diseases. Previously, he developed the newborn screening for six lysosmal storage diseases- Gaucher's, Krabbe (or globoid cell leukodystrophy), Pompe, Niemann-Pick, Fabry's, and Hurler's. Since 2009, New York, Missouri, and Kentucky use the newborn screening Dr. Gelb developed. Illinois, New Mexico, New Jersey, Pennsylvania, Ohio and Tennessee have also passed legislation to add these screenings, with implementation dates varying by state.
Newborn screening represents a game-changing moment for leukodystrophy and similar diseases. While a viable newborn screening remains years away, the pilot is an exciting development. But, there is no question patient and family advocates will have a crucial role to play in lobbying states to include MLD newborn screening in state-mandated testing and encouraging regional hospitals to participate.
This is an important first step, but there is much work to be done.
*To measure the characteristics of individual molecules, a mass spectrometer converts them to ions so that they can be moved about and manipulated by external electric and magnetic fields. To assist state agencies in efficacious newborn screening, it is critical to ensure additional funding for equipment accompanies legislation for newborn screening.