Nelson Textbook of Pediatrics 22nd Edition — Dystrophinopathies: X-linked (Xp21). DMD: onset 2-5y, CK >10,000, calf hypertrophy, Gowers sign, loss of ambulation ~12y. BMD: milder, ambulatory into adulthood. Corticosteroids, exon skipping, gene therapy (Elevidys), cardiac surveillance.
🌐 paeds.online — Pakistan's Pediatric Platform| Feature | Duchenne MD (DMD) | Becker MD (BMD) |
|---|---|---|
| Onset | 2-5 years | >5-7 years (often >12 years) |
| Incidence | 1 in 3,600 males | 1 in 30,000 males |
| Walking delay | ~50% delay past 18 months | Often normal |
| Gowers sign | Evident by age 3-6 years | Later or absent |
| Loss of ambulation | ~10-14 years (with steroids, later) | Often ambulatory into adulthood |
| CK level | 15,000-35,000 IU/L | 1,000-15,000 IU/L |
| Dystrophin protein | Absent (<3%) | Reduced or abnormal (20-90%) |
| Genetic defect | Out-of-frame deletions (65%) | In-frame deletions (preserve reading frame) |
| Cardiomyopathy | Majority, progresses after loss of ambulation | Common, may develop while ambulatory |
| Intellectual impairment | ~20-30% IQ <70 | Less common |
| Lifespan (untreated) | Late teens to 20s | 40s-50s (cardiac complications) |
Corticosteroids: Prednisone 0.75 mg/kg/day or deflazacort 0.9 mg/kg/day. Prolong ambulation by 2-3 years, slow scoliosis, preserve pulmonary function. Vamorolone (new corticosteroid) approved for ≥2 years.
Exon skipping antisense oligonucleotides: Eteplirsen (Exondys 51, exon 51, ~13%), golodirsen (Vyondys 53, exon 53, ~8%), viltolarsen (Viltepso, exon 53).
Ataluren: Readthrough for nonsense mutations (10-15% of DMD).
Gene therapy: Elevidys (delandistrogene moxeparvovec) — AAV-delivered micro-dystrophin, FDA approved for children 4-5 years old.