New test spots early signs of inherited metabolic disorders

A team of scientists, led by researchers at the University of California, San Diego School of Medicine and Zacharon Pharmaceuticals, have developed a simple, reliable test for identifying biomarkers for mucopolysaccharidoses (MPS), a group of inherited metabolic disorders that are currently diagnosed in patients only after symptoms have become serious and the damage possibly irreversible.

The findings will be published online 8 January in the journal Nature Chemical Biology.

MPS is caused by the absence or malfunctioning of a lysosomal enzyme required to break down and recycle complex sugar molecules called glycosaminoglycans, which are used to build bone, tendons, skin and other tissues.

 If not degraded and removed, glycosaminoglycans can accumulate in cells and tissues, resulting in progressive, permanent damage affecting appearance, physical abilities, organ function and often mental development in young children. The effects range from mild to severe.

There are 11 known forms of MPS, each involving a different lysosomal enzyme. A number of treatments exist, including enzyme replacement therapy and hematopoietic stem cell transplantation, but efficacy depends upon diagnosing the disease and its specific form as early as possible. That has been problematic, said Jeffrey D. Esko, PhD, professor in the department of cellular and molecular medicine and co-director of the Glycobiology Research and Training Centre at UC San Diego.

''The typical time from seeing first symptoms to diagnosis of MPS is about three years. Since the early signs of disease are common childhood issues like ear infections and learning disorders, the disease is usually not immediately recognized,'' Esko said.