Duchenne muscular dystrophy (DMD) is inherited as an X-linked recessive disorder, though one-third of cases are spontaneous mutants. DMD occurs in 1 in 3000 male infants.
The Duchenne muscular dystrophy locus has been localized to the Xp21 region of the X chromosome; there is absence of the gene product - the protein dystrophin , which is a rod-shaped cytoskeletal muscle protein. DMD is usually obvious by the fourth year, and often causes death by 20.
Sign and Symptom of Duchenne muscular dystrophy
Dystrophin is essential for cell membrane stability, and deficiency leads to reduction in three glycoproteins (now called a-, ß- and ?-sarcoglycan) which link dystrophin to laminin within the cell membrane.
The boy with DMD is noticed to have difficulty in running and in rising to an erect position from the floor, when he has to use the hands to climb up his legs (Gowers' sign).
There is initially a proximal limb weakness with pseudohypertrophy of the calves. The myocardium is affected. The boy becomes severely disabled by the age of 10.
Differential diagnosis of Duchenne muscular dystrophy
- biopsy remains the most effective test for differentiating the various muscular dystrophies;
- Myopathic Disorders
- Becker Muscular Dystrophy
- Facioscapulohumeral Muscular Dystrophy
- Limb Girdle