Myopathies and other causes of muscle weakness Flashcards
What are the 6 inflammatory myopathies?
A OPIoID
- Antisynthetase Syndrome
- Overlap Myositis
- Polymyositis
- IBM
- Immune mediated necrotizing myopathy
- Dermatomyositis
One fact about Polymyositis
Rare. Diagnosis of exclusion.
One fact about Dermatomyositis
Assess for cancer (multiple different types)
One fact about Inclusion Body Myositis
Not immune mediated
One fact about Immune mediated necrotizing myopathy
Statins can trigger it
One fact about Antisynthetase syndrome
Look for mechanic’s hands
One fact about Overlap myositis
Associated with other connective tissue disorders
What is the best screening test for acid maltase deficiency
- Dried blood spot to measure GAA activity
- Would need confirmatory genetic testing
- AKA Pompe disease
What will the EMG show on acid maltase deficiency (Pompe disease)?
- Myotonic discharges
- Fibs
- Small, short and polyphasic MUAPs
- Typically seen in paraspinal, abdominal and very proximal muscles
What is the genetic abnormality in myotonic dystrophy?
CTG tri-nucleotide expansion in the myotonin protein kinase gene
What types of PN do CMT1 and CMT2A respectively?
- CMT1 = demyelinating
- CMT2A = axonal
What are the 8 clinical conditions that can occur with an HTLV-1 infection
- Myelopathy
- Peripheral neuropathy
- Radiculopathy
- Cranial neuropathies
- Polymyositis
- Meningitis
- Cerebellar ataxia
- Encephalopathy
In the ischemic forearm test, what are the results for the following conditions?
- Myophosphorylase deficiency
- Phosphofructokinase deficiency
- Myoadenylate deaminase deficiency
- Insufficient effort from the patient
- Phosphoglycerate kinase deficiency
- Mitochondrial myopathy
- Myophosphorylase deficiency = ammonia increases
- Phosphofructokinase deficiency = ammonia increases
- Myoadenylate deaminase deficiency = lactate increases
- Insufficient effort from the patient = neither ammonia or lactate increases
- Phosphoglycerate kinase deficiency = ammonia increases
- Mitochondrial myopathy = ammonia increases
When ammonia increases but lactate doesn’t it suggests a glycogen storage disease or a disorder of glycolysis
In what conditions will you see an amyloid myopathy?
(Deposited along muscle fiber surfaces & in Perimysium)
- Hereditary amyloidosis (transthyretin or gelsolin)
- Primary amyloidosis (light-chain amyloidosis)
- It is uncommon in secondary amyloidosis
Fibs and positive sharp waves can be seen in what types of myopathies? What kind will they not be seen in?
Fibs and positve sharp waves seen in toxic, inflammatory and necrotizing myopathies. Also some glycogen storage diseases.
They are not seen in steroid myopathies
Seen on muscle biopsy:
Fiber type grouping (Type I and Type II in separate groups)
Suggests chronic reinnervation
(below is normal checkerboard pattern)
Seen on muscle biopsy:
Perifascicular atrophy
Dermatomyositis
Seen on muscle biopsy:
Glycogen positive vacuoles on right
Vacuolated muscle fibers on left
Pompe disease (acid maltase deficiency)
Seen on muscle biopsy:
Rimmed vacuoles
Inclusion body myositis
Seen on muscle biopsy:
Necrotic fibers
Necrotizing myopathy
