Screening people with muscle weakness, damage identifies LOPD
Early detection can help patients get treatment sooner, researchers say
Screening people with unexplained muscle weakness or elevated levels of muscle damage markers can help to identify people with late-onset Pompe disease (LOPD), a study found.
The study, “Screening for Pompe disease in Serbian patients with limb-girdle muscle weakness,” was published in Clinical Neurology and Neurosurgery.
LOPD is characterized by Pompe disease symptoms that develop after the first year of life. An earlier age at symptom onset is generally associated with a faster rate of disease progression. In some people with the condition, symptoms don’t become apparent until adulthood — and since symptoms like muscle weakness are seen in many other disorders besides LOPD, it can be hard to pinpoint the disease.
Scientists in Serbia conducted a study in which 138 people were screened for LOPD over the course of 4.5 years. Reasons for testing were mainly unexplained weakness in shoulder and hip muscles, unexplained weakness in muscles needed to breathe, and/or unexplained high levels of creatine kinase, a marker of muscle damage. Fourteen participants were tested for other reasons, including muscle aches and exercise intolerance, calf enlargement, and heart muscle disease associated with elevated levels of creatine kinase.
Measuring enzyme activity
Pompe disease is caused by mutations in the GAAÂ gene, which provides instructions to make an enzyme called acid alpha-glucosidase. As part of the program, enzyme activity was measured first, and 10 patients (7.2%) were found to have low enzyme activity.
These 10 were referred for genetic testing of the GAA gene, and ultimately four of them were found to have Pompe-causing mutations. These four patients had lower GAA enzyme activity than all others in whom an LOPD diagnosis was excluded.
Four confirmed cases out of 138 tested works out to a total rate of LOPD of 2.9%. The 134 people tested who did not have LOPD were ultimately found to have other diseases that cause muscle weakness, such as muscular dystrophy or amyotrophic lateral sclerosis.
The four people confirmed to have LOPD started treatment with enzyme replacement therapy, which has been proven to slow progression of the disease.
The researchers noted that the average time between the onset of symptoms and LOPD testing was about eight years. “It is important to shorten this period since [enzyme replacement therapy] that significantly changes the course of LOPD is available,” the scientists wrote, noting that “evidence suggests that earlier initiation of therapy has a more profound impact on improving muscle function and slowing disease progression.”
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