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DMD and BMD in the same family due to distinct mutations
L Morandi1, M Mora, S Tedeschi
1Department of Neuromuscular Disorders, National Neurological Institute C. Besta, Milan, Italy.
American Journal of Medical Genetics
|December 4, 1995
Summary
Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy can arise from distinct dystrophin gene deletions within the same family. Genetic testing in at-risk males may reveal these separate mutations, even in asymptomatic individuals.
Area of Science:
- Genetics
- Molecular Biology
- Neuromuscular Disorders
Background:
- Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are allelic disorders caused by mutations in the dystrophin gene.
- These X-linked recessive disorders affect skeletal muscle, leading to progressive muscle weakness and degeneration.
Observation:
- A family presented with a boy diagnosed with Duchenne muscular dystrophy (DMD).
- An asymptomatic cousin was incidentally found to have a Becker-type dystrophin abnormality.
Findings:
- Dystrophin gene analysis revealed two distinct deletions, each with breakpoints in different exons, responsible for the DMD and Becker-type phenotypes.
- The identified mutations were associated with separate haplotypes within the Xp21 region.
Implications:
- DNA and dystrophin testing in asymptomatic males within Xp21 families, particularly those with elevated creatine kinase (CK) levels, can identify distinct dystrophin mutations.
- Such genetic investigations should be guided by clear clinical or familial indications to ensure appropriate diagnostic yield.