Researchers led by a University of Washington biochemist have developed the first screening for newborns that can detect metachromatic leukodystrophy, a rare degenerative cognitive condition.
The findings were published Jan. 4 in Clinical Chemistry.
In cases of metachromatic leukodystrophy, or MLD, a genetic deficit causes a fatty substance, sulfatide, to accumulate in the brain and peripheral nervous systems. This accumulation destroys myelin, the protective sheathing around nerves, disrupting signals that govern motor movements and cognitive skills. Ultimately the condition causes death.
The incidence of MLD 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 those in conditions far more common.
About 60 percent of the people diagnosed with MLD are babies aged 12-24 months; an additional 20 to 30 percent are diagnosed between age 3 and teen years, and the remainder are diagnosed as adults. Earlier onset correlates with faster disease progression.
The new finding means it is possible to detect MLD’s genetic deficit at birth, which would enable infants to receive future therapies before brain damage occurs – but only if the screening were to become part of the panel of tests given to newborns, which varies among states.
“It’s early days for this,” said Michael Gelb, a UW professor of chemistry and adjunct professor of biochemistry. An enzyme specialist, Gelb led development of the MLD screening.
“We usually screen for conditions for which there are treatment options,” he said. “We moved on this because in a recent clinical trial, gene therapy appears to be effective against the disease. The treatment seems to work so well that interest in newborn screening is escalating.”
Currently, MLD is diagnosed biochemically by analyzing urine samples for the elevated presence of sulfatides.
Using mass spectrometry, his team developed a technique to extract sulfatides from dried blood samples, and detected meaningful concentrations of the substance. Further, the scientists were able to stratify sulfatide levels and associate them with disease severity.
“Nobody in the U.S. is going to start collecting urine samples for one disease. But now we can detect elevated sulfatides in dried blood, which opens the possibilities for newborn screenings.”
The next step is a large pilot study of the screening. It will last a couple of years and include “maybe 80,000 or 100,000 samples,” Gelb said, to get a sense of the false-positive rate across a broad genotypic scale.
“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.”
In any case, any rare diseases would need grassroots support from parents and communities to galvanize state agencies to add a new screening to newborn disease panels.
Source: University of Washington