Myopathy Flashcards
What are the three major groups of myopathies?
- Muscular dystrophies (dystrophic: fiber splitting + ^ CT)
- Inflammatory myopathies
- Metabolic myopathies
Duchenne Muscular Dystrophy:
- Inheritance
- Chromosome
- Onset
- Initial Weakness
- Rate of progression
- CK
- EKG
- Muscle biopsy?
- XR; 1/3 spontaneous
- Xp21, large deletion
- Onset 5 yoa
- Pelvic weakness first; (+) Gower’s sign
- Rapidly progressive
- ^^^CK
- Abnormal EKG
- Muscle biopsy shows MQ invasion, necrotic fibers
Becker Muscular Dystrophy:
- Inheritance
- Chromosome
- Onset
- Initial Weakness
- Rate of progression
- CK
- EKG
- XR; Xp21
- Onset 10 yoa
- Pelvic weakness first
- Slower progression
- ^^CK (more moderate)
- Abnormal EKG
Face-Scapulo-Humoral
- Inheritance
- Chromosome
- Onset
- Initial Weakness
- Rate of progression
- CK
- EKG
- AD; chromosome 4
- Onset 10-20 yoa
- Initial shoulder weakness w/ early facial weakness
- Slow progression
- Normal CK and EKG
Myotonic Muscular Dystrophy
- Inheritance
- Chromosome
- Onset
- Initial Weakness
- Rate of progression
- CK
- EKG
- AD; chromosome 19
- Onset 15-30 yoa
- DISTAL weakness first** w/ early facial weakness
- Slow progression
- Normal CK w/ abnormal EKG
Limb Girdle Muscular Dystrophy
- Inheritance
- Chromosome
- Onset
- Initial Weakness
- Rate of progression
- CK
- EKG
- AR or AD; mult. chroms
- Onset 10-30 yoa
- Pelvic- shoulder weakness first; spares the face
- Slowly progressive
- ^ CK
- Occasionally abnormal EKG
Compare the pathophys of Duchenne and Becker’s musculodystrophy: which mutations are in frame vs. out of frame?
- Duchenne is out of frame
- Beckers is in frame
Both result in deficient dystrophin, weak sarcolemma, and muscle necrosis
What are the clinical features of Duchenne’s Muscular Dystrophy?
- Waddling gait, pseudo hypertrophy of calves, lumbar lordosis, weak neck flexors
- Wheel chair at 13 yoa
- Cognitive impairment
- GI pseudoobstruction
- Cardiomyopathy and death by 20yoa form cardio/resp failure
How do we treat Duchennes?
Steroids; delazacort at 4yoa
What are the clinical features of a DMD carrier; how many carriers demonstrate sx?
- 8% have sx
- Asstd with X inactivation: patients have mild myalgia, CVD, Cognitive, bx issues
- ^ CK, ^ aldolase
Describe how Beckers differed from DMD:
- Onset 12 yoa; ambulatory into adulthood; live beyond 30 yoa
- Less likely cognitive, CVD, contractors, scoliosis, GI issues
Facioscapulomumoral MD:
What are the clinical features?
Slowly progressive wasting of facial, scapular, humeral, and perineal muscles (winged scapula)
No reduction in life expectancy
List some features of Myotonic Dystrophy 1 that differentiate it from Myotonic dystrophy 2: (4)
MD1:
- Distal weakness
- Congenital; DMPK gene; anticipation
- Cataracts, Cardio problems
- MR, avoidant personality
What differentiates Myotonic Dystrophy 2 from Myotonic dystrophy 1?
MD2:
- Proximal weakness
- Rare; zinc finger protein 9 gene mutation
Limb Girdle MD:
- What are the general features of this disease
- Two common comorbidities
- Pace of the typical course
- Which is dominant and which is recessive?
Slowly progressive hip and shoulder weakness
Commonly comorbid with cardiorespiratory problems
Slowly progressive, symmetric, proximal
Type 1 is dominant; type 2 is recessive
Emmy Dreifuss MD, Type 1 vs Type 2:
- What are the mutant proteins
- What is the inheritance pattern
- Which has contractures?
- What is a common comorbidity associated with both?
- 1 = Emerin; 2 = Lamin A/C
- Type 1 always XR; type 2 may be dominant or recessive
- Type 1 has contractures before weakness
- Both have cardiac comorbitities; type 1 specifically conduction abnormalities
Oculopharyngeal Muscular Dystrophy:
- Inheritance pattern
- Age of onset
- Clinical features
- Treatment
- AD; onset in middle age
- Ptosis, EOM and limb weakness, dysphagia
- Treat with oculoplasty and PEG
Dermatomyositis:
- Rash?
- Location of weakness?
- Age of onset? Population?
- Asstd w cancer?
- Response to steroids?
- CK?
- EMG
- Muscle biopsy findings
- Rash present
- Proximal weakness
- Bimodal onset: kids, 40+
- Asstd w breast cancer; Women»>
- Good response to steroids
- ^ CK
- Myopathic EMG
- Muscle biopsy = perifasicular atrophy
Polymyositis:
- Rash?
- Location of weakness?
- Age of onset? Population?
- Asstd w cancer?
- Response to steroids?
- CK?
- EMG
- Muscle biopsy findings
- NO RASH
- Proximal weakness
- Adult onset; Women»>
- Asstd w cancer
- Variable response to steroids
- ^ CK
- Myopathic EMG
- Endopysial Inflammation
Inclusion Body Myositis:
- Rash?
- Location of weakness?
- Agoe of onset? Population
- Asstd w cancer?
- Response to steroids?
- EMG
- Muscle biopsy findings
- NO RASH
- DISTAL–> Proximal weakness; asymmetric
- Onset 50+ yoa; Men»>
- NO assn w cancer
- Myopathic + neuropathic EMG findings
- Amyloid Inclusion bodies + rimmed vacuoles on biopsy
Which of the inflammatory myopathies can not be treated with immunosuppression?
Inclusion body; does not respond well
List the three glycogenoses myopathies:
- McArgles (myophosphorylase)
- Pompe’s (acid maltase)
- PFK deficiency
List the 2 lipidoses myopathies:
- Carnitine Deficiency
- Carnitines Palmityl Transferase Deficiency
What are the two channelopathies that cause myopathy?
What are the channels that they compromise?
What are the triggers for sx?
- Hyperkalemic periodic paralysis (SCN4A channels)–triggered by rest after fasting or exercise; better w/ fasting and exercise
- Hypokalemic periodic paralysis (L type Ca channels):
Weakness lasting hrs or days w carboloading or exercise
Three metabolic myopathies:
- Kearns-Sayre Syndrome
- MERRF
- MELAS
Glycogen and Lipid Myopathies:
- Inheritance pattern
- Clinical présentation
- Most are AR
- Present w exercise intolerance, post-exercise myoglobinuria, ^ CK
How does Pompe’s present?
Proximal weakness; resp insufficiency
How does Cori’s present?
Distal weakness; cardiomyopathy, PN
Which glycogen storage diseases present with exercise intolerance and myoglobinuria?
How are they differentiated?
McArdles, PFK
McArdles has second wind phenomenon
When do patients with lipid storage diseases experience symptoms?
What are the sx? (5)
Flare ups w fasting
Proximal weakness, tender muscles, ^ CK, recurrent myoglobinuria, lipid vacuoles on biopsy
Provoked necrotizing polymyopathy/ Rhabdomyolysis with myoglobinuria
What is the cause?
What are the sx?
How do we treat it?
Caused by ETOH abuse or crush injury
Presents with pihgmeturia, swollen/ tender muscles
Treat with IVF, CK monitoring, +/- dialysis
Patients with a defect in what enzyme are predisposed to malignant hyperthermia?
Phosphodiesterase
How does hypothyroid myopathy present? (5)
- muscle cramps
- mild proximal weakness
- delayed reflexes
- myoedema on percussion
- ^ CK
How does Critical Illness Myopathy present?
What is the cause?
Patients with sepsis/ malnutrition/ etc + paralytics, steroid tx in ICU–> Myopathy w loss of myosin on biopsy
What type of weakness is caused by acromegaly and cushings?
proximal; Cushing’s is more in lower extremities
Describe the findings on a myopathic EMG
Low amplitude, short duration, polyphasic waves with rapid recruitment
Steroid myopathy results in what type of weakness?
proximal
What are some drugs other than steroids that result in myopathy (3)
- Statins (no mevalonic acid)
- AZT
- Rheumatology drugs
Which is the most common overall muscular dystrophy?
Duchenne
Which is the most common muscular dystrophy in adults?
Myotonic Dystrophy 1
Which dystrophy is normally recessively inherited?
LGMD type II
Which type of dystrophy does not involve the cardiac muscle?
Oculopharyngeal muscular dystrophy
In a patient with “biopsy proven polymyositis” who does not respond to conventional treatments, what alternative disorder is most likely?
Inclusion body myositis
Which muscular dystrophy is associated with a triplet repeat?
Oculopharyngeal muscular dystrophy; GCG
Which muscular dystrophy is associated with rimmed vacuoles on muscle biopsy?
Inclusion body myositis
