A new set of laboratory tests using gene sequencing is able to help confirm 24 lysosomal storage diseases, providing physicians and patients the tools for much more accurate and rapid diagnosis. Lysosomal storage diseases are a group of more than 40 inherited and potentially life-threatening disorders that cause enzymes to malfunction in cellular compartments called lysosomes. This leads to the accumulation of waste products that damage organs and tissues.
The gene sequencing tests, developed by scientists in Emory University's Genetics Laboratory, are available to clinicians throughout the country, and can be used for clinical diagnosis, carrier testing for family members and prenatal testing. Emory Genetics Laboratory offers the most comprehensive list of sequencing tests in the country for lysosomal storage diseases, according to Vanessa Rangel Miller, MS, CGC.
"Before the availability of our tests, there were far fewer sequencing and DNA-based tests for lysosomal storage disorders," she said. "This limited many families who did not have the option for carrier and prenatal testing. In the past, some carrier and prenatal tests were performed using less accurate biochemical methods" according to Madhuri Hegde, PhD, FACMG, co-director, Emory Genetics Laboratory. Emory Genetics Laboratory includes six board certified laboratory directors and four board-certified genetic counselors.
The prevalence of lysosomal storage disorders in the United States is 1 out of 7,000 newborns. Tests for lysosomal storage disorders typically are ordered by general internists, cardiologists, nephrologists, gastroenterologists, geneticists, metabolic specialists and others caring for children and adults suspected of having a lysosomal storage disorder, or by obstetricians or prenatal genetics counselors who have patients with a family history of these disorders.
Physicians in Emory's Lysosomal Storage Disease Center, established in 1993 in the Department of Human Genetics, diagnose, evaluate, and treat patients using a variety of treatment regimens, including the most advanced enzyme replacement technologies, which over the past 15 years have changed the lives of many patients. The Emory center is one of only two centers nationally with an infusion center within a department of genetics. The center combines diagnosis and treatment with laboratory research and clinical trials aimed at learning even more about these inherited diseases.
Lysosomal storage diseases are difficult to identify because symptoms often mimic those of more common diseases, and symptoms may develop very gradually. Patients often visit many physicians before their condition is accurately diagnosed. Early diagnosis is critically important, however, because progressive accumulation of waste material in cells can cause irreversible damage. Some symptoms are considered hallmarks of lysosomal storage diseases. These include unusual facial features, an enlarged tongue, cloudiness in the eyes, a purplish-blue skin rash, distended belly, failure to grow, and muscle weakness or decline in motor skills.
Type I Gaucher disease was the first genetic disorder that could be treated effectively with enzyme replacement therapy (ERT). Over the past decade, ERT has become available for Fabry disease, Mucopolysaccharidosis Type VI (MPS VI - Maroteaux-Lamy), and MPS I (Hurler, Hurler-Scheie, or Scheie syndrome). ERT also is in development for other lysosomal storage conditions including Pompe (also known as glycogen storage disease type II), MPS II (Hunter syndrome), Niemann-Pick Disease, and MPS IV (Morquio syndrome).