Muscular dystrophies result from genetic defects in structural proteins of the muscle resulting in weak structure of the muscles. This weak structure of the muscles leads to inability of the muscles to bear the stress, which consequently leads to loss of muscle fibers and their replacement with fibrous tissue. Duchenne muscular dystrophy is one of many dystrophies and is relentless in the sense that it starts early in life and progresses fairly quickly.
1. Cause:
Duchenne muscular dystrophy is a hereditary disorder of skeletal muscles and involves other types of muscles during later stages of disease. It is an X-linked recessive disorder with chromosomal abnormality located at Xp21 gene.
2. Pathophysiology:
Dystrophin-glycoprotein complex is a protein complex found in the sarcolemma (covering membrane of the muscle fiber) that connects the contractile apparatus of the muscle fiber with the extracellular matrix. Since Duchenne muscular dystrophy is a disorder predominantly of quantity (absence) of dystrophin hence it leads to disruption of the cellular structure of the muscle resulting in its death and destruction.
3. Clinical Features:
I. Onset:
It starts very early during the childhood, usually before 5 years of age and is noticed by the parents first of all as frequent falls.
II. Mobility:
Child becomes wheel chair bound by early teens.
III. Other Features:
Later child develops multiple other features including pseudo-hypertrophy of muscles, scoliosis, contractures, respiratory difficulty and eventually failure.
IV. Cardiac Involvement:
Cardiac muscle can also be affected, which eventually leads to cardiac failure.
V. Gower’s Sign:
Gower’s sign is inability to stand up from sitting position on the ground without support of the hands and upper limbs.
