DUCHENNE MUSCULAR DYSTROPHY (DMD) (26 exons)

The dystrophin (DMD) gene is one of the largest in the human genome, containing 79 exons. Mutations or deletions in these exons disrupt dystrophin protein production, leading to Duchenne muscular dystrophy. Diagnostic genetic testing identifies which specific exons are affected to guide prognosis and treatment options such as exon skipping therapies.

Exon 51 is one of the 79 exons in the dystrophin gene. Deletions around exon 51 are common in DMD, and skipping this exon during treatment can restore the reading frame of the gene, enabling the body to produce a shorter but functional dystrophin protein. This approach benefits about 13% of DMD patients with specific deletion patterns.

Deletions in DMD most frequently occur between exons 45–55, especially 45–50, 48–50, or 49–52. These deletions disrupt the reading frame of the dystrophin gene, preventing functional protein synthesis. Genetic testing using MLPA or sequencing determines the exact exons missing, which helps predict severity and identify eligibility for exon-skipping therapies.

Exon skipping is a targeted therapy that uses synthetic molecules (antisense oligonucleotides) to make the cellular machinery skip over faulty or missing exons during mRNA processing. This restores the genetic reading frame, allowing partial production of dystrophin. It doesn’t cure DMD but can slow disease progression and improve muscle stability.

The DMD gene contains a total of 79 exons, while some smaller genes have far fewer. Exon numbers vary widely among human genes depending on their size and complexity. The DMD gene spans about 2.2 million base pairs—making it the largest known human gene—with each exon contributing to functional protein assembly.

Yes, DMD caused by certain deletions such as exons 45–50, 47–50, or 49–50 can benefit from exon 51 skipping. This restores the reading frame of the dystrophin mRNA, allowing partial protein production. FDA-approved drugs like eteplirsen target exon 51 skipping and are suitable for patients with specific mutation patterns confirmed through genetic testing.