DMD

Question 1

DMD Etiology

Answer 1

• X linked recessive disorder
• gene Xp21 discovered 1982
• Absence of large muscle protein: Dystrophin in 1987
• Affects Skeletal and Cardiac muscle
• affects 1/3500 males
• 100% lethal

Question 2

Dystrophen

Answer 2

• found on the cytoplasmic surface of muscle cell membrnes
• key building block to muscle fibers
• Function: to stabilize the plasma membrane, provides mechanical reinforcement to the sarcolemma and protect the membrane from stresses during muscle contraction.

Question 3

Diagnosis

Answer 3

Diagnosis

• Blood tests: elevated CK levels
• muscle biopsy shows necrosis and regeneration, variation in muscle fiber size, increased type 1 fibers, increased connective tissue with fat infiltration, increased # of macrophages

Clinical Signs

• gower’s sign
• coordination problems
• clumsiness
• enlarged calf;s

Question 4

Disease Progression DMD

Answer 4

• Damage to sarcolemma: begins process of inflammation with increased # of macrophages to cell signaling
• satellite cells migrate to the area: fuse and repair of fibers
• Cycle of: repair-damage-repair
• unable to keep up with the repair process due to lack of dystrophin to stabilize the membrane
• muscle becomes infiltrated with fat and firbrotic tissue

Question 5

Damage of DMD

Answer 5

• mechanically induced damage: eccentric>concentric>isometric contractions
• down stream events: altered regeneration, inflammation, impaired vascular adaptation (lack of O2) and fibrosis

Question 6

Effect on Life and Dx Progression

Answer 6

• Proximal muscles are the first to show weakness
• leads to changes in posture and difficulty with daily activities
• wheelchair required by mid to early teens
• shortened life expectancy early to mid 20s

Question 7

Current Therapies for DMD

Answer 7

1. Dystrophin gene delivery
2. correction of mutant dystrophin RNA/DNA
3. cell based therapies-delivery of normal cells to dystrophic muscle

Question 8

Rehabilitation with DMD

Answer 8

• preserving ROM - no over stretching and no deep tissue work that will cause damage
• balance - ankle strategy, trunk reactions to maintain midline and current posture
• respiratory care - assistive cough, positioning, CPT
• swimming
• other - biking

Question 9

Contraindications

Answer 9

NO RESISTIVE EXERCISE

NO ECCENTRIC CONTRACTIONS