Duchenne Muscular Dystrophy is a disease of –
DUCHENNE MUSCULAR DYSTROPHY (PSEUDO HYPERTROPHIC MUSCULAR DYSTROPHY)

Duchenne muscular dystrophy is the most common hereditary neuromuscular disease affecting all races and ethnic groups.
Inheritance: X linked recessive
Presentation occurs between ages 3 and 5 


Pathogenesis

Duchenne muscular dystrophy is caused by a mutation in the gene responsible for producing dystrophin.
Dystrophin is `subsarcolemmal protein' localized to the inner surface of the sarcolemma of the muscle fibre.
Dystrophin is part of Dystrophin - Glycoprotein sarcolenzmal complex and this protein deficiency leads to secondary loss of sarcoglycans and dystroglycans resulting in weakness of sarcolemma, causing membrane tears and muscle fibre necrosis.

Clinical manifestations:

Gower's sign is positive
Pseudohypertrophy of the calf is seen (muscle is replaced by fat & connective tissue)
Loss of muscle strength is progressive.
Proximal muscles and neck flexors are involved more
Leg involvement is more severe than arm involvement.
Contractures of heel cords and iliotibial band occurs (by age of 6 years)
progressive scoliosis develops.

Complications:

Chest deformity (scoliosis): Impairs pulmonary function By age of 16 and 18 years patients are predisposed to serious pulmonary fatal infections.
Cardiac: Cardiomyopathy and CHF may be seen Cardiac cause of death is uncommon
Intellectual impairment: is common (IQ is one SD below the mean)
Neuromuscular junction
Sarcolemmal proteins
Muscle contractile proteins
Disuse atrophy due to muscle weakness