BMD is associated with the DMD gene, located on the X chromosome. The packet lists DMD as the only gene for this condition and does not include a ClinGen validity classification for it. GeneReviews states that the dystrophinopathies are inherited in an X-linked manner, and the packet's inheritance field lists X-linked inheritance. According to GeneReviews, the reading frame rule holds that pathogenic variants that do not alter the reading frame (in-frame deletions or duplications) generally correlate with the milder BMD phenotype, whereas variants that alter the reading frame generally correlate with the more severe DMD phenotype. GeneReviews reports that this rule distinguishes the two phenotypes with 91% to 92% accuracy in young children who are simplex cases, that exceptions are documented, and that exceptions may be more frequent for the BMD phenotype, particularly with duplications. GeneReviews further states that phenotypes are best correlated with the degree of dystrophin expression. Penetrance is described as complete in males, while penetrance in heterozygous females varies and may depend in part on patterns of X-chromosome inactivation. GeneReviews also notes that a male who is the only affected family member may have a de novo variant.

GeneReviews states that a dystrophinopathy is suspected on the basis of the clinical findings above, especially with a positive family history compatible with X-linked inheritance, and that the presence of fasciculations or loss of sensory modalities excludes a suspected diagnosis of a dystrophinopathy. Laboratory testing described by GeneReviews includes serum CK concentration, which is elevated in 100% of affected males, at approximately 5 times normal for BMD, and which gradually decreases with advancing age. In female carriers, elevated CK is reported in approximately 30% for BMD, at 2 to 10 times normal. GeneReviews states that in a male proband the diagnosis is established by characteristic clinical findings with elevated CK concentration and/or by identification of a hemizygous pathogenic or likely pathogenic variant in DMD on molecular genetic testing. In a female proband, the diagnosis is usually established by characteristic clinical findings with elevated CK and/or a heterozygous pathogenic or likely pathogenic DMD variant. GeneReviews notes that the distinction between DMD and BMD can be difficult in some cases.

The packet does not certify any FDA-approved treatment record with active market status for BMD. The packet's orphan drug records list many products with orphan designation for Becker or Duchenne muscular dystrophy; orphan designation does not establish approval, development status, or efficacy. GeneReviews states that appropriate management of individuals with a dystrophinopathy can prolong survival and improve quality of life. For cardiomyopathy in DMD and BMD, GeneReviews reports that the authors' institution commonly treats children early with an ACE inhibitor and/or beta blocker, that angiotensin II-receptor blockers are similarly effective and can be used when ACE inhibitors are poorly tolerated, that other heart failure therapies are used in overt heart failure, and that cardiac transplantation is offered to persons with severe dilated cardiomyopathy and BMD with limited or no clinical evidence of skeletal muscle disease. GeneReviews also describes scoliosis management in DMD and BMD, involving bracing and surgery. Its corticosteroid discussion is specific to DMD. GeneReviews initial evaluations for individuals with a dystrophinopathy include a physical therapy assessment, a developmental evaluation before elementary school for an individualized educational plan, cardiomyopathy evaluation by electrocardiography, echocardiography and/or MRI, and involvement of a clinical geneticist and/or genetic counselor. For surveillance in BMD, GeneReviews describes complete cardiac evaluation at least every two years beginning at diagnosis. Under investigation, GeneReviews describes gene therapy approaches using recombinant adeno-associated virus vectors that deliver micro- or minidystrophin genes or gene-editing components.

GeneReviews describes the course of BMD mainly through the age of wheelchair dependency, which occurs after age 16 years, with some individuals remaining ambulatory into their 30s and in rare cases into their 40s and beyond. GeneReviews reports that cardiac involvement is the cause of death in approximately 50% of individuals with BMD, compared with approximately 20% of individuals with DMD. For DMD-associated dilated cardiomyopathy in males, GeneReviews describes rapid progression with onset in the teenage years, and notes that appropriate management of dystrophinopathies can prolong survival. Individual courses are not predicted by the packet, and no survival figures specific to BMD are certified in it.

ClinicalTrials.gov records in this packet show an active research area for the condition, with a mixed sponsor profile and trial interventions classified as drug therapy, gene therapy, medical devices and other interventions. Records specific to BMD include NCT05257473, titled Defining Endpoints in Becker Muscular Dystrophy, sponsored by Virginia Commonwealth University and listed as active, not recruiting; and NCT07740057, a multimodal study about absence of Dp140 in Becker muscular dystrophy using brain-muscle imaging, cognition and muscle function, sponsored by Institut de Myologie, France and listed as not yet recruiting. NCT07378553, sponsored by Nantes University Hospital and listed as recruiting, addresses ultrafast ultrasound biomarkers for Duchenne and Becker muscular dystrophies. The trial titles do not establish the effect of any intervention. Active clinical trials for this condition are listed on ClinicalTrials.gov. The packet's research landscape digest classifies the publication literature as predominantly basic science and preclinical, with gene therapy and biomarker publications present.