BECKER DIAGNOSIS

Having an accurate, timely diagnosis is a critical aspect of care. There are reliable tests to help confirm the diagnosis of a person with Becker muscular dystrophy. The following tests are typically used to confirm a preliminary diagnosis.

CREATINE KINASE (CK) BLOOD TEST

If your family doctor suspects that you or your child has a medical problem in the muscles, it is likely that your family doctor will order a CK (creatine kinase, sometimes referred to as a CPK or creatine phosphokinase) blood test as a first step in the diagnostic process.

CK is an enzyme that normally lives inside muscles. In healthy muscle, the membrane surrounding the muscle is intact, keeping the CK inside. In Becker, the lack of functional dystrophin keeps the muscle from tolerating the constant muscle movement of everyday activities, giving rise to tiny tears in the damaged muscle membrane. When this happens, CK leaks out of the muscle and into the blood.

The CK level of a person who does not have dystrophinopathy (Duchenne/Becker) is usually less than 200 units/liter. Elevated CK levels indicate a problem with the muscles (rather than a problem with the nerves, for example), although a high CK does not confirm a diagnosis of Becker, and is not genetic testing. CK levels in individuals with Becker may be mildly elevated, sometimes much less so than an individual with Duchenne.

If you/your child have an elevated CK test, your doctor should offer you testing that can give a diagnosis. The two types of tests that are used to make a diagnosis are genetic testing and muscle biopsy. Learn about CK testing here.

GENETIC TESTING

Genetic testing is the best way to obtain exact genetic information for a conclusive Becker diagnosis. DNA-based genetic testing is used to find variants (changes) in the gene that codes for dystrophin, the DMD gene.

There are different genetic testing methods that find different types of variants., and some people may need more than one test to confirm their diagnosis.If a person with Becker has a complete set of genetic tests, it is very likely that the lab will find a variant. If the lab finds a variant, most individuals will not need to have a muscle biopsy. Learn more about genetic testing and PPMD’s free genetic testing program, Decode Duchenne.

MUSCLE BIOPSY

If genetic testing is not able to accurately provide a diagnosis, a muscle biopsy may be performed. A muscle biopsy (a surgical procedure that involves taking a small sample of muscle for analysis) looks for changes in the amount and look of dystrophin protein. This is usually done by immunohistochemistry of slides of the muscle (putting a stain on the muscle, then looking at the muscle cells under a microscope for evidence of dystrophin) or by a Western blot test of the muscle protein (a chemical process that tests for the chemical presence of dystrophin). This type of testing can usually tell whether a person has Duchenne or Becker muscular dystrophy, however is not always conclusive. Because this is a surgical procedure, it is more invasive than a blood test.

MAKING INFORMED CHOICES

Every primary care provider has a different amount of experience with Becker and with genetic testing. Some will know how to help you make informed choices about the pros and cons of muscle biopsy and genetic testing, and others may not. Many primary care providers will refer you to a neuromuscular or genetics specialist for diagnosis and testing and for long term management. If you have any concerns after meeting with the specialist, a second opinion may be useful. Informing yourself is always a good way to help promote good health care for your family.

If you are unsure of where to find a specialist, you can see a list of PPMD’s Certified Duchenne Care Centers or email careteam@parentprojectmd.org and we are happy to assist with finding a provider close to you. 

Genetic Counselors

Genetic counselors are excellent resources for assisting with the decision of whether to test for a diagnosis, getting a second opinion, the best tests to choose and how to understand the results. If you have questions, please contact your local genetic counselor.