General Considerations

  • Since Becker is a progressive, irreversible disease, early diagnosis has important implications in terms of disease management and progression. 4
  • Becker muscular dystrophy can go undiagnosed or be misdiagnosed as other dystrophies or myopathies, with similar signs and symptoms. 3
  • Even though an individual’s clinical presentation, along with an elevated circulating creatine kinase level is often suggestive of Becker, genetic testing to identify a pathogenic variation in the DMD (dystrophin) gene is recommended to confirm a diagnosis. 3
Nevin
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According to the Cooperative International Neuromuscular Research Group (CINRG) Becker Natural History Study, median duration of symptoms prior to diagnosis was 2 years, with 25% ≥ 5 years and 12% ≥ 10 years.18

Diagnosing Becker Muscular Dystrophy

Due to the multi-systemic, progressive nature of Becker muscular dystrophy, early diagnosis and early intervention with multidisciplinary team management are paramount for optimal care.1,3,4

*Diagnosing Becker

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#Patient Assessment 3

The typical individual with Becker muscular dystrophy is a young man with one or more of the following:

  • Progressive weakness in pelvic girdle muscles
  • Calf hypertrophy
  • Family history of Becker or Duchenne muscular dystrophy
  • Cramps after physical exercises
  • Dilated cardiomyopathy

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#Lab Tests

Individuals living with Becker present with elevated levels of biomarkers of muscle injury. 1

Elevated serum CK

  • CK Plasma levels are usually >5x normal levels (>1000 IU/L). 1,3
  • In some cases, >10,000 IU/L, even in those with normal muscle strength and endurance.3,4

CK levels are higher early in the disease process and decrease progressively as muscle is replaced with fat.3

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#Genetic Testing

The diagnosis of Becker in suspected individuals can be established by the identification of a pathogenic variant in the DMD (dystrophin) gene.1,3

Genetic testing can involve 2 steps

  • Conduct genetic testing for mutations in the DMD (dystrophin) gene3.
  • In the absence of abnormality in the coding sequence, extracting messenger RNA (mRNA) data from muscle biopsy to search for rearrangements in the coding sequences. 3

An in-frame mutation, or the combination of out-of- frame mutation with maintained ambulation past 16 years of age without use of steroids supports the diagnosis of Becker muscular dystrophy.3

*Based on the French Guidelines for Becker muscular dystrophy

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High CK levels are helpful, and the diagnosis can be confirmed by muscle biopsy and, more specifically, by the identification of a pathogenic variation in the DMD gene.3

Becker Muscular Dystrophy Functional Tests After Establishing Diagnosis

Functional Tests

Establishing an individual’s baseline is important for long term disease monitoring. A variety of functional tests can be considered, including the following:3

North Star Ambulatory Assessment (NSAA)

A global assessment scale, the NSAA measures the ability to conduct several activities. Specifically, this test measures an individual’s ability to perform 17 assessments which tests the speed and functionality of their motor skills. 8

Composite evaluation of motor function across 17 tests with increasing difficulty
Real-world implications for Becker individuals

Recent guideline suggests these assessment in clinical practice after establishing diagnosis should be considered3

  • The North Star Assessment for limb-girdle type muscular dystrophies (NSAD).
    A 29-item scale of motor performance for both ambulatory and non-ambulatory individuals.8

  • Timed function tests.
    Measures walking time over 10 or 100 meters, and time required to conduct daily movements (e.g. climbing steps, getting up from a lying position, etc.).

  • The 6-min walk test.
    Measures walking distance in 6 minutes.

  • Brooke and Vignos scales.
    These functional measures evaluate the progression of arm and leg weakness, respectively.

  • Motor function measurement scale (MFM).
    It consists of over 20 items that score the ability of an individual to conduct daily gestures from 0 (unable to perform the movement) to 3 (normal gesture).

  • Evaluation of muscle strength by manual testing (MRC score).
    The MRC scale for muscle strength uses manual muscle testing to grade muscle strength, ranging from a 0 to 5 point scale.

NSAA & NSAD Functional Measures
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It is recommended that functional tests remain consistent within each institution to allow for comparison of progression over time.3

Additional Testing Recommendations After Establishing Diagnosis

Cardiac

  • Based on a 2023 guideline by the French BMD Working Group, an electrocardiogram (ECG) and an echocardiogram are recommended for initial cardiac assessment, as heart failure is the most common cause of premature death in individuals living with Becker.1,3
  • Cardiac magnetic resonance imaging (CMRI) is also recommended at diagnosis as it estimates cardiac function more accurately than echocardiography and is more sensitive than ECG at detecting early myocardial fibrosis.3,20
  • If the above tests show the presence of an abnormality in cardiac systolic function (I.e., left ventricular ejection fraction <50%) or significant conduction defects, a 24-h Holter ECG is recommended. This will not only reveal any ventricular or supraventricular arrhythmias, if present, but will also serve as a baseline reference during the follow-up.3

Neuropsychological and Respiratory

  • Neuropsychological assessment
    As individuals living with Becker can present with cognitive and neuropsychological disorders more so than the general population, a cognitive or psychiatric assessment by a neuropsychologist at diagnosis is recommended.3
  • Respiratory assessment
    Individuals living with Becker may experience declining respiratory function, therefore initial assessments of inspiratory and expiratory muscles, and pulmonary function testing are recommended.3
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Since heart failure is the most common cause of premature death in individuals living with Becker, an electrocardiogram (ECG) and an echocardiogram are recommended at the time of diagnosis.1,3