DMD one of themost common lethal genetic disease of childhood. It
is the most common and most devastating
of the muscular dystrophies, that affects all ethnicities, nationalities
and socioeconomic groups, although it occurs almost exclusively in
males. It is inherited as an x-linked disease that is characterized
by a rapidly progressive muscle weakness. Children with DMD show early
signs of muscle weakness and begin walking relatively late in childhood.
They develop a waddling gait and have difficulty in climbing stairs.
Their muscles show a false or pseudo-hypertrophy, most notably in
the calf muscles, where the muscles appear large but are actually
replaced by fat or fibrous tissue.
Becker muscular dystrophy (BMD) results from mutations in the same
gene as DMD but follows a milder clinical course, with later development
of weakness and loss of function.
occurs in ~1:3500 male births world-wide and ~1:5000 in developed
countries that provide genetic counseling. In ~70% of the cases, the
mother of the affected child is a carrier of the disease. In the remaining
30% of cases, the disease results from a new mutation. If the mother
is a carrier, there is a 50% chance for each of her male children
to have DMD, and a 50% chance for each female offspring to be a carrier.
Genetic counseling is recommended if there is a family history of
DMD. Mutations in the gene that cause DMD can be detected with approximately
95% accuracy in prenatal testing.