Duchenne muscular dystrophy is a genetic disorder causing progressive muscle weakness. It’s the most common type of muscular dystrophy, affecting about one in 3,500 boys.
A mutation in the gene responsible for producing dystrophin, a protein crucial for muscle cell health, causes Duchenne muscular dystrophy. Without proper dystrophin, muscle cells over time become fragile and degenerate.
This weakness emerges in the legs and pelvis around the age of four, then spreads to the arms, making it hard to maintain an upright position. By twelve, most patients require wheelchairs.
Muscle symptoms you might notice:
- Motor delay: a delay in acquiring motor skills.
- Progressive muscle weakness.
- Hypotonia: abnormally low muscle tone. Even when relaxed, muscles have a continuous and passive partial contraction, which provides some resistance to passive stretching.
- Calf muscle hypertrophy: increased size of calf muscles.
- Cardiomyopathy: heart muscles that are structurally and functionally abnormal (in the absence of coronary artery disease, hypertension, valvular disease and congenital heart disease) that cause the observed myocardial abnormality.
- Flexion contracture: a bent (flexed) joint that cannot be actively or passively straightened.
- Hyporeflexia: reduction of neurologic reflexes such as the knee-jerk reaction.
- Tip-toe gait: abnormal gait pattern characterised by the failure of the heel to contact the floor at the onset of stance.
- Waddling gait: weakness of the hip girdle and upper thigh muscles, which leads to an instability of the pelvis on standing and walking.
- Loss of ambulation: inability to walk in a person who previously could walk.
Other symptoms you might notice:
Abnormal lateral curvature of the spine (scoliosis); delayed speech and language development; impairment of certain skills, like reading, writing, self-control or attention, that interfere with the ability to learn; cognitive impairment; mild intellectual disability; obstructive sleep apnea.
Genetic treatments for Duchenne muscular dystrophy.
Researchers are conducting extensive studies to enhance treatments. Gene therapy, specifically exon skipping, shows great potential. Exon skipping means bypassing a specific gene segment, called an exon, to correct mutations that cause the dystrophin gene to be out-of-frame. This permits the gene to be restored, albeit with a gap. Keep in mind that not everyone can use exon skipping therapies since they only work for certain out-of-frame mutations.
Right now, there are four approved treatments that can fix the dystrophin gene and maybe stop or slow down the disease.
- Vyondys 53 (golodirsen) injection
- Viltepso (vitolarsen) injection
- Amondys 45 (casimersen) injection
- Exondys 51 (eteplirsen) injection
With continued research and clinical trials, all children with Duchenne muscular dystrophy may one day live longer, healthier lives.
