Myopathies Flashcards
What is the Ddx for weakness?
- Metabolic disturbances due to endocrine/electrolyte abnormalities
- Systemic illness from infection, immunologic or neoplastic origin
- UMN disease
- Neuromuscular disease
What is a myopathy?
A disease of muscles resulting in weakness and variable pain and wasting
What are the three types of myopathies?
- Muscular dystrophy
- Inflammatory myopathies
- Metabolic myopathies
What features are associated with dystrophic myopathies?
- Fiber splitting
2. Increased connective tissue
What are the different types of muscular dystrophy?
- Duchenne
- Becker
- Fascio-scapulo-humeral (FSH)
- Myotonic
- Limb girdle
- Emery-Dreifuss
- Oculo-pharyngeal
What are the main areas of weakness in Duchenne MD?
Proximal upper and lower limbs
What are the main areas of weakness in Emery-Dreifuss MD?
Proximal upper limb and distal lower limb
What are the main areas of weakness in Limb Girdle MD?
Proximal upper and lower limbs
What are the main areas of weakness in Fascio-scapulo-humeral (FSH) MD?
Proximal upper limbs + calfs + face
What are the main areas of weakness in Oculopharyngeal MD?
Proximal upper and lower limbs + eyes + throat
Describe the genetics and onset of Duchenne’s MD
X-Linked recessive
Xp21 large deletion
Onset at age 5
Describe the genetics and onset of Becker MD
X-Linked recessive
Xp21
Onset at age 10
Describe the genetics and onset of FSH MD
Autosomal Dominant
Chromosome 4
Onset 10-20
Describe the genetics and onset of Myotonic MD
Autosomal Dominant
Chromosome 19
Onset 15-30
Describe the genetics and onset of Limb Girdle MD
AR/AD
Onset 10-30
What is the initial weakness in Duchenne’s MD?
Pelvic- will have Gower’s Sign
What is the initial weakness in Becker’s MD?
Pelvic
What is the initial weakness in FSH MD?
Shoulder
What is the initial weakness in Myotonic MD?
Distal Weakness
What is the initial weakness in Limb Girdle MD?
Pelvic-Shoulder
Which muscular dystrophies show early facial weakness?
FSH and Myotonic MD
Which muscular dystrophies show late facial weakness?
Duchenne and Becker MD
Which MD spares the face?
Limb Girdle MD
Which muscular dystrophy has a rapid progression?
Duchenne’s MD
Which muscular dystrophies have elevated CK?
Duchenne + Becker + Limb Girdle
Which MD has a normal EKG?
FSH
Describe the muscle histology for Duchenne MD
Macrophage invasion + necrotic fibers
Patholophysiological difference between Duchenne and Beckers MD
Duchenne = Out of Frame mutation in Dystrophin Beckers = In frame mutation in Dystrophin
What is the consequence of mutated Dystrophin?
It weakens the sarcolemma and leads to muscle necrosis
What are the clinical features of Duchenne’s MD?
- Difficulty running, waddling gait
- Calf Pseudohypertrophy
- Neck flexor weakness
- Lumbar Lordosis
- CI
- Wheel chair by 13
- Intestinal pseudo-obstruction
- Cardiomyopathy –> HF
- Respiratory failure
Typical age of death in patient with DMD?
20
What is the treatment for Duchenne’s MD?
- Prednisone
2. Deflazacort (best started by age 4-7)
How do steroids benefit patients with DMD?
- Prolong ambulation
- Delay respiratory failure
- Stabilize the sarcolemma
- Increase muscle mass
Why are 8% of female carriers of DMD symptomatic?
X-linked inactivation turns off the healthy dystrophin gene
What is the typical presentation in symptomatic female carriers of DMD?
- Mild risk of heart disease, muscle weakness and CI
- Myalgia
- Elevated CK and aldolase
Compare the symptoms of Becker’s MD to DMD
Beckers presents with calf pseudohypertrophy and early thigh weakness, but patients are less likely to have the GI obstruction, heart failure, CI and contractures seen in DMD patients
What will EMG show for DMD and Becker’s MD?
Myopathic Units
What are non-medical treatments appropriate for Becker’s MD?
- Genetic Counseling
- Physical Therapy
- Orthopedic Complication
What is the genetic association with fascioscapulohumeral MD?
Autosomal Dominant deletion of D4Z4 on 4q35
Describe the symptoms of FSH MD
Slow wasting of facial, scapular, humeral and perineal muscles, down sloping shoulders + winged scapular and prominent clavicles
Is life expectancy altered in FSH MD?
No
Which muscle groups are affected by Myotonic Dystrophy 1?
Distal Muscle Groups
Which muscle groups are affected by Myotonic Dystrophy 2?
Proximal Muscle Groups
Which type of Myotonic Dystrophy is more common?
Type 1
What is the genetic association with the different types of Myotonic Dystrophy?
Type 1: CTG repeats in DMPK gene
Type 2: CCTG repeats in zinc finger protein 9
Which hereditary pattern is seen with Myotonic Dystrophy Type 1?
Anticipation
What are symptoms of Myotonic Dystrophy Type 1?
- Myotonia
- Cataracts
- Avoidant Personality
- Hypersomnia
- Hypogonadism
- Mental Retardation
- Cardiac issues
What is the genetic pattern observed in Limb Girdle Muscular Dystrophy Types 1 and 2?
Type 1: AD
Type 2: AR
Other than proximal muscles, which organ systems may be involved in LGMD?
Cardiac and Respiratory Systems