General considerations

  • Becker muscular dystrophy is an X-linked recessive disease caused by mutations in the DMD gene, affecting approximately 1:18,000 male births.4,7
  • Since Becker is a progressive, irreversible disease, early diagnosis has important implications in terms of disease management and progression.6,7
  • Becker muscular dystrophy can go undiagnosed or be misdiagnosed as other dystrophies or myopathies, with similar signs and symptoms.4
  • 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.4
Jess, an adult living with muscular dystrophy, sitting on his couch composing music

Jess lives with Becker muscular dystrophy and came to New York to become a music composer and an improv comic.

#

According to data from the Duchenne Registry for Duchenne and Becker muscular dystrophy (BMD), median duration of symptoms prior to diagnosis was 2 years, with 25% ≥5 years and 12% ≥10 years.27

Diagnosing Becker muscular dystrophy*

Due to the multisystemic, progressive nature of Becker muscular dystrophy, early diagnosis and early intervention with multidisciplinary team management are paramount for optimal care.3,4,7

1

#Patient Assessment4

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

2

#Lab Tests

Individuals living with Becker present with elevated levels of biomarkers of muscle injury.4

Elevated serum creatine kinase (CK)

  • CK plasma levels are usually >5x normal levels (>1000 IU/L).3,4
  • CK levels can be elevated even in those with normal muscle strength and endurance.4

CK levels are higher early in the disease process and decrease progressively as muscle is replaced with fat.4

3

#Genetic Testing

The diagnosis of Becker in suspected individuals can be established by the identification of a pathogenic variant in the DMD (dystrophin) gene.4

Genetic testing can involve 2 steps

  • Conduct genetic testing for mutations in the DMD (dystrophin) gene.4
  • In the absence of abnormality in the coding sequence, extracting messenger RNA (mRNA) from muscle biopsy to search for rearrangements in the coding sequences.4

Diagnosis can be established by the presence of an in-frame mutation, or the combination of out-of-frame mutation with maintained ambulation beyond 16 years of age without steroid use.4

*Based on the French Guidelines for Becker muscular dystrophy.

#

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.

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 following4:

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 test the speed and functionality of their motor skills.10

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

Along with the NSAA, a recent guideline suggests the following standardized assessments for consideration4

  • 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.19

  • Timed function tests.
    Measures walking time over 10 or 100 meters, and time required to conduct daily movements (eg, climbing steps, getting up from a lying position, etc).19

  • 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
#

It is recommended that functional tests remain consistent within each institution to allow for comparison of progression over time.4

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.3,4
  • 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.4
  • If the above tests show the presence of an abnormality in cardiac systolic function (ie, 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.4

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.4
  • 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.4
#

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.3,4